U.S. investigators suspect that Malaysia Airlines Flight 370 stayed in the air for up to four hours past the time it reached its last confirmed location, according to two people familiar with the details, raising the possibility that the plane could have flown on for hundreds of additional miles under conditions that remain murky. 
 
 The investigators believe the plane flew for a total of up to five hours, according to these people,... ||||| Story highlights U.S. Navy commander: Expanding search is "going from a chess board to a football field" 
 
 U.S. official: "Probably a significant likelihood" plane is at the bottom of the Indian Ocean 
 
 Communications systems were shut down separately 
 
 Officials to CNN: "Pings" of data were sent hours after the last transponder signal 
 
 It's a mystery that authorities still haven't been able to solve: Where is Malaysia Airlines Flight 370? 
 
 There were still more questions than answers Thursday as U.S. officials said investigators will start combing the Indian Ocean as they look for the missing aircraft. 
 
 Why would authorities expand their search rather than narrowing it? 
 
 New information, U.S. officials told CNN, indicates the missing airplane could have flown for several hours beyond the last transponder reading. 
 
 Malaysian authorities believe they have several "pings" from the airliner's service data system, known as ACARS, transmitted to satellites in the four to five hours after the last transponder signal, suggesting the plane flew to the Indian Ocean, a senior U.S. official told CNN. That information combined with known radar data and knowledge of fuel range leads officials to believe the plane may have made it to that ocean, which is in the opposite direction of the plane's original route. 
 
 "There is probably a significant likelihood" that the aircraft is now on the bottom of the Indian Ocean, the official said, citing information Malaysia has shared with the United States. 
 
 Photos: The search for MH370 Photos: The search for MH370 Two years after Malaysia Airlines Flight 370 went missing, a relative of one of the passengers burns incense in Beijing on March 8, 2016. Flight 370 vanished on March 8, 2014, as it flew from Kuala Lumpur, Malaysia, to Beijing. There were 239 people on board. Hide Caption 1 of 43 Photos: The search for MH370 On July 29, police carry a piece of debris on Reunion Island, a French territory in the Indian Ocean. A week later, authorities confirmed that the debris was from the missing flight. Hide Caption 2 of 43 Photos: The search for MH370 Staff members with the Australian Transport Safety Bureau examine a piece of aircraft debris at their laboratory in Canberra, Australia, on July 20. The flap was found in June by residents on Pemba Island off the coast of Tanzania, and officials had said it was highly likely to have come from Flight 370. Experts at the Australian Transport Safety Bureau, which is heading up the search for the plane, confirmed that the part was indeed from the missing aircraft. Hide Caption 3 of 43 Photos: The search for MH370 In late February, American tourist Blaine Gibson found a piece of plane debris off Mozambique, a discovery that renewed hope of solving the mystery of the missing flight. The piece measured 35 inches by 22 inches. A U.S. official said it was likely the wreckage came from a Boeing 777, which MH370 was. Hide Caption 4 of 43 Photos: The search for MH370 Relatives of the flight's passengers console each other outside the Malaysia Airlines office in Subang, Malaysia, on February 12, 2015. Protesters had demanded that the airline withdraw the statement that all 239 people aboard the plane were dead. Hide Caption 5 of 43 Photos: The search for MH370 A police officer watches a couple cry outside the airline's office building in Beijing after officials refused to meet with them on June 11, 2014. The couple's son was on the plane. Hide Caption 6 of 43 Photos: The search for MH370 Members of the media scramble to speak with Azharuddin Abdul Rahman, director general of Malaysia's Civil Aviation Department, at a hotel in Kuala Lumpur, Malaysia, on May 27, 2014. Data from communications between satellites and the missing flight was released the day before, more than two months after relatives of passengers said they requested it be made public. Hide Caption 7 of 43 Photos: The search for MH370 Operators aboard the Australian ship Ocean Shield move Bluefin-21, the U.S. Navy's autonomous underwater vehicle, into position to search for the jet on April 14, 2014. Hide Caption 8 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks out of a window while searching for debris off the coast of western Australia on April 13, 2014. Hide Caption 9 of 43 Photos: The search for MH370 The HMS Echo, a vessel with the British Roya; Navy, moves through the waters of the southern Indian Ocean on April 12, 2014. Hide Caption 10 of 43 Photos: The search for MH370 A Royal Australian Air Force AP-3C Orion, on a mission to drop sonar buoys to assist in the search, flies past the Australian vessel Ocean Shield on April 9, 2014. Hide Caption 11 of 43 Photos: The search for MH370 A relative of a missing passenger cries at a vigil in Beijing on April 8, 2014. Hide Caption 12 of 43 Photos: The search for MH370 Australian Defense Force divers scan the water for debris in the southern Indian Ocean on April 7, 2014. Hide Caption 13 of 43 Photos: The search for MH370 A towed pinger locator is readied to be deployed off the deck of the Australian vessel Ocean Shield on April 7, 2014. Hide Caption 14 of 43 Photos: The search for MH370 A member of the Royal New Zealand Air Force looks at a flare in the Indian Ocean during search operations on April 4, 2014. Hide Caption 15 of 43 Photos: The search for MH370 On March 30, 2014, a woman in Kuala Lumpur prepares for an event in honor of those aboard Flight 370. Hide Caption 16 of 43 Photos: The search for MH370 The sole representative for the families of Flight 370 passengers leaves a conference at a Beijing hotel on March 28, 2014, after other relatives left en masse to protest the Malaysian government's response to their questions. Hide Caption 17 of 43 Photos: The search for MH370 A member of the Royal Australian Air Force is silhouetted against the southern Indian Ocean during the search for the missing jet on March 27, 2014. Hide Caption 18 of 43 Photos: The search for MH370 Flight Lt. Jayson Nichols looks at a map aboard a Royal Australian Air Force aircraft during a search on March 27, 2014. Hide Caption 19 of 43 Photos: The search for MH370 People in Kuala Lumpur light candles during a ceremony held for the missing flight's passengers on March 27, 2014. Hide Caption 20 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, delivers a statement about the flight on March 24, 2014. Razak's announcement came after the airline sent a text message to relatives saying it "deeply regrets that we have to assume beyond any reasonable doubt that MH 370 has been lost and that none of those onboard survived." Hide Caption 21 of 43 Photos: The search for MH370 Grieving relatives of missing passengers leave a hotel in Beijing on March 24, 2014. Hide Caption 22 of 43 Photos: The search for MH370 A passenger views a weather map in the departures terminal of Kuala Lumpur International Airport on March 22, 2014. Hide Caption 23 of 43 Photos: The search for MH370 A Chinese satellite captured this image, released on March 22, 2014, of a floating object in the Indian Ocean, according to China's State Administration of Science. It was a possible lead in the search for the missing plane. Surveillance planes were looking for two objects spotted by satellite imagery in remote, treacherous waters more than 1,400 miles from the west coast of Australia. Hide Caption 24 of 43 Photos: The search for MH370 Satellite imagery provided by the Australian Maritime Safety Authority on March 20, 2014, showed debris in the southern Indian Ocean that could have been from Flight 370. The announcement by Australian officials raised hopes of a breakthrough in the frustrating search. Hide Caption 25 of 43 Photos: The search for MH370 Another satellite shot provided by the Australian Maritime Safety Authority shows possible debris from the flight. Hide Caption 26 of 43 Photos: The search for MH370 A distraught relative of a missing passenger breaks down while talking to reporters at Kuala Lumpur International Airport on March 19, 2014. Hide Caption 27 of 43 Photos: The search for MH370 On March 18, 2014, a relative of a missing passenger tells reporters in Beijing about a hunger strike to protest authorities' handling of information about the missing jet. Hide Caption 28 of 43 Photos: The search for MH370 U.S. Navy crew members assist in search-and-rescue operations in the Indian Ocean on March 16, 2014. Hide Caption 29 of 43 Photos: The search for MH370 Members of the Chinese navy continue search operations on March 13, 2014. After starting in the sea between Malaysia and Vietnam, the plane's last confirmed location, search efforts expanded west into the Indian Ocean. Hide Caption 30 of 43 Photos: The search for MH370 A Vietnamese military official looks out an aircraft window during search operations March 13, 2014. Hide Caption 31 of 43 Photos: The search for MH370 Malaysian air force members look for debris near Kuala Lumpur on March 13, 2014. Hide Caption 32 of 43 Photos: The search for MH370 Relatives of missing passengers wait for the latest news at a hotel in Beijing on March 12, 2014. Hide Caption 33 of 43 Photos: The search for MH370 A member of the Vietnamese air force checks a map while searching for the missing plane on March 11, 2014. Hide Caption 34 of 43 Photos: The search for MH370 A Vietnamese air force plane found traces of oil that authorities had suspected to be from the missing Malaysia Airlines plane, the Vietnamese government online newspaper reported on March 8, 2014. However, a sample from the slick showed it was bunker oil, typically used to power large cargo ships, Malaysia's state news agency, Bernama, reported on March 10, 2014. Hide Caption 35 of 43 Photos: The search for MH370 A U.S. Navy Seahawk helicopter lands aboard the USS Pinckney to change crews on March 9, 2014, before returning to search for the missing plane in the Gulf of Thailand. Hide Caption 36 of 43 Photos: The search for MH370 Buddhist monks at Kuala Lumpur International Airport offer a special prayer for the missing passengers on March 9, 2014. Hide Caption 37 of 43 Photos: The search for MH370 Members of a Chinese emergency response team board a rescue vessel at the port of Sanya in China's Hainan province on March 9, 2014. Hide Caption 38 of 43 Photos: The search for MH370 The rescue vessel sets out from Sanya in the South China Sea on March 9, 2014. Hide Caption 39 of 43 Photos: The search for MH370 Malaysian Prime Minister Najib Razak, center, arrives to meet family members of missing passengers at the reception center at Kuala Lumpur International Airport on March 8, 2014. Hide Caption 40 of 43 Photos: The search for MH370 A relative of two missing passengers reacts at their home in Kuala Lumpur on March 8, 2014. Hide Caption 41 of 43 Photos: The search for MH370 Chinese police at the Beijing airport stand beside the arrival board showing delayed Flight 370 in red on March 8, 2014. Hide Caption 42 of 43 Photos: The search for MH370 Malaysia Airlines Group CEO Ahmad Juahari Yahya, front, speaks during a news conference at a hotel in Sepang on March 8, 2014. "We deeply regret that we have lost all contacts" with the jet, he said. Hide Caption 43 of 43 
 
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 It's the latest twist in a case that's baffled investigators and grabbed global attention for days since the plane disappeared on its way from Kuala Lumpur to Beijing. Information about the missing flight has been hard to come by, and numerous leads have been revealed by some officials only to be debunked by others hours later. 
 
 This new information led to a decision to move the USS Kidd into the Indian Ocean to begin searching that area, the official said. 
 
 The Navy destroyer is now on its way there at the request of the Malaysian government, Cmdr. William Marks of the U.S. 7th Fleet told CNN's Wolf Blitzer Thursday. 
 
 "We're not out here freelancing, and it's not just something the U.S. Navy thinks and no one else," Marks said. "So this was by request of the Malaysian government. They asked the Navy to move our ship to the west into the Strait of Malacca. ... It is coordinated, but certain ships and aircraft stay in the east, and some go to the west. And we're moving to the west." 
 
 It won't be easy. Moving into the Indian Ocean, Marks said, is like going "from a chess board to a football field." 
 
 The Indian Ocean is the world's third largest ocean, and in most places it's much deeper than other areas where search crews have been looking. 
 
 "It's a completely new game. ... Now we have to come up with a new strategy, new tactics," he said. 
 
 Conflicting reports cloud investigation 
 
 There are conflicting reports about this latest lead as well. 
 
 Earlier Thursday the Malaysian government denied a Wall Street Journal report that the plane was transmitting data after the last transponder signal. 
 
 And a senior aviation source with detailed knowledge of the matter also told CNN's Richard Quest on Thursday that there was no technical data suggesting the airplane continued flying for four hours, and said specifically that the Wall Street Journal account was wrong. 
 
 But U.S. officials maintained Thursday afternoon that the information from the airplane's data system was being actively pursued in the plane investigation. 
 
 Analysts from U.S. intelligence, the Federal Aviation Administration and the National Transportation Safety Board have concluded that the pings likely came from the missing aircraft, the senior U.S. official said. 
 
 There is reason to believe the plane flew for four hours, officials said, but there is no specific indication where the plane actually is. 
 
 Multiple bursts of data were received indicating the plane was flying over the Indian Ocean, the senior U.S. official told CNN. 
 
 But there's another confusing twist. An emergency beacon that would have sent data upon impact apparently did not go off, the official said. The beacons, known as Emergency Locator Transmitters, activate automatically upon immersion in fresh or salt water, but must remain on the surface for a distress signal to transmit. 
 
 The failure of the beacon to activate could mean that the plane didn't crash, that the transmitter malfunctioned, or that it's underwater somewhere. 
 
 Mary Schiavo, former inspector general for the U.S. Department of Transportation, said even though it's unclear how accurate the latest information is, authorities have no choice but to pursue it. 
 
 "Well I think basically given that there is some information -- how reliable or not -- we have to respond," she said. "There is no way we cannot follow up on this lead. It would be inhumane. And it might turn out to be just the lead we need. ... There isn't much, but I think we have to do it." 
 
 So are we any closer to knowing whether a mechanical problem, terrorism or hijacking could be tied to the plane's disappearance? 
 
 Not really, said Evy Poumpouras, a former Secret Service agent. 
 
 "The sad thing here is, we don't have enough information to say, 'It's not this, it's not that,'" she told CNN's Don Lemon. "We're still at the point, six days later, it could be anything, and that's the frustrating thing." 
 
 Analyst: 'Deliberate act' shut down communication 
 
 Another detail that emerged Thursday seemed to add a new twist to the mystery. Malaysian officials said two separate communications systems stopped 14 minutes apart. 
 
 The officials said the plane's data reporting system shut down at 1:07 a.m. Saturday, while the transponder transmitting location and altitude shut down at 1:21 a.m. 
 
 "This is beginning to come together to say that ...this had to have been some sort of deliberate act" and not a catastrophic failure, ABC News aviation analyst John Nance told CNN's Erin Burnett. 
 
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 White House spokesman Jay Carney didn't go into details when he discussed the search for the plane Thursday, but he said "some new information that's not necessarily conclusive" could lead U.S. searchers to the Indian Ocean. 
 
 "We are looking at information, pursuing possible leads, working within the investigation being led by the Malaysian government, and it is my understanding that one possible piece of information or collection of pieces of information has led to the possibility that a new search area may be opened," Carney said. 
 
 Originally, a report from The Wall Street Journal said data from the plane's Rolls-Royce engine had raised questions among some U.S. officials about whether the plane had been steered off course "with the intention of using it later for another purpose," the newspaper reported, citing a "person familiar with the matter." 
 
 The newspaper later corrected its story, saying that data leading investigators to believe the plane had flown for up to five hours came from the plane's satellite-communication link, which the newspaper said is "designed to automatically transmit the status of certain onboard systems to the ground." 
 
 Malaysia's acting Transportation Minister Hishammuddin Hussein rejected the Wall Street Journal report at a news conference Thursday, reiterating that the plane sent its last transmissions at 1:07 a.m. Saturday. 
 
 And Malaysia Airlines Chief Executive Ahmad Jauhari Yahya said that Rolls-Royce and Boeing have reported that they didn't receive transmissions of any kind after 1:07 a.m. Saturday. Air traffic controllers lost contact with the plane shortly afterward, around 1:30 a.m. 
 
 Erin Atan, a spokeswoman for Rolls-Royce in Asia, declined to comment on the matter, telling CNN it was "an official air accident investigation." 
 
 Authorities have not ruled out the possibility the plane continued to fly, however. And given the lack of evidence, all options remain on the table. 
 
 Four more hours in the air could have put the plane many hundreds of miles beyond the area currently being searched. 
 
 But one aviation industry observer expressed skepticism about the report even before the denials by officials. 
 
 "I find this very, very difficult to believe," Tom Ballantyne, chief correspondent for the magazine Orient Aviation, told CNN. "That this aircraft could have flown on for four hours after it disappeared and not have been picked up by someone's radar and not have been seen by anyone, it's almost unbelievable." 
 
 Search getting harder 
 
 The mystery over the fate of the passenger jet, a Boeing 777-200, and the 239 people it was carrying has so far left government officials and aviation experts flummoxed. 
 
 "With every passing day the task becomes more difficult," Hishammuddin said. 
 
 Searchers have already been combing a vast area of sea and land for traces of the plane. But so far, after six days of searching, their efforts have been fruitless. 
 
 The news came after Vietnamese and Chinese search crews found nothing where Chinese satellite photographs released Wednesday showed large floating objects in the South China Sea. 
 
 Chinese officials originally described the images as showing "a suspected crash site" between Malaysia and Vietnam, not far from the plane's expected flight path. 
 
 But Hishammuddin later said the images didn't actually show any debris relating to the plane. 
 
 Malaysian officials say they are still trying to determine if a radar blip detected heading west soon after the plane lost contact was in fact the missing jet. 
 
 If it was, the plane would have been hundreds of miles off its original flight path and headed in the wrong direction. Malaysian officials say they have asked U.S. experts to help them analyze the radar data. 
 
 Meanwhile, India is joining the multinational search, dispatching two of its naval ships off the remote Andaman and Nicobar islands, a military spokesman told CNN. 
 
 Last known words 
 
 Also on Thursday, a Malaysian aviation official told CNN that the last known words from the flight crew of the missing plane were "All right, good night." 
 
 Malaysian civil aviation officer Zulazri Mohd Ahnuar said he couldn't confirm which member of the flight crew sent the message, which was transmitted from the plane back to Malaysian flight controllers as the aircraft transferred into Vietnamese airspace early Saturday. 
 
 Malaysian officials on Thursday denied reports that police had searched the homes of the crew members who were on the plane. 
 
 Hishammuddin said the reports were "not true." 
 
 A source close to the family of Capt. Zaharie Ahmad Shah, the pilot of the missing plane, told CNN that police have been outside Zaharie's home every day since Saturday. The police haven't asked to come inside but were on the street as recently as Thursday morning taking photos of the house, the source said. 
 
 Another source, who is familiar with the vicinity of the property, told CNN that police have been seen on the street outside the home every day since Sunday. 
 
 For the families of those on board the missing plane, the wait for news is torturous. 
 
 Danica Weeks is trying to keep it together for her two young sons, though the possibility of life without husband Paul, who was on the plane, is sometimes overwhelming. She's clinging to hope even though, as Weeks told CNN's Piers Morgan , it's "not looking good." 
 
 "Every day, it just seems like it's an eternity, it's an absolute eternity," Weeks said from Australia. "We can only go minute by minute ... and hope something comes soon."
– The mystery of Malaysia Airlines Flight 370 has become even more baffling: US investigators believe the plane flew on for four hours after its last contact with air traffic controllers, meaning it could be anywhere in a huge area ranging from India to Australia to the southern tip of Japan, according to a report in the Wall Street Journal that cites "two people familiar with the details." But Malaysia's transportation minister wasted no time in quashing the WSJ report; calling it "inaccurate," he claims that both Boeing and Rolls Royce (the maker of the engines) also deny it, and says no transmissions were received from the plane after it lost contact, CNN reports. The Journal's sources say aviation investigators base their belief on data automatically transmitted from the Boeing 777's engines to the ground. An aviation industry observer had already thrown cold water on the report, noting that it was "almost unbelievable" the plane could have flown for that long without being spotted or picked up by any radar. Vietnamese and Malaysian authorities, meanwhile, have found no trace of debris where satellite images indicated there could be floating pieces of the plane.