( CNN ) -- The United States warned the Indian government about a potential maritime attack against Mumbai at least a month before last week 's massacre in the country 's financial capital left nearly 180 dead , a U.S. counterterrorism official told CNN . Onlookers in Mumbai read messages posted outside the Oberoi Hotel , scene of one of the attacks . U.S. intelligence indicated that a group might enter the country by water and launch an attack on Mumbai , said the source , who refused to be identified due to the ongoing investigation into the attacks and the sensitivity of the information . Indian security forces have confirmed to CNN that not only did U.S. officials warn them of a water-borne attack in Mumbai -- they were told twice . The area entered a higher state of alert for a week , including tightened security measures at hotels , but those efforts were eventually reduced , Indian officials said . Local fisherman in Mumbai said they witnessed a group of gunmen dock their boat Wednesday night , before heading toward the busy causeway . Also , sources have told CNN-IBN that officials found phones and a global navigational device on an abandoned boat floating off the coast of Mumbai . The boat had been hijacked , intelligence officials told CNN-IBN . Watch Nic Robertson 's report about U.S. warning . Four crew members who had been on board were missing . The captain was found dead , lying face down with his hands bound behind his back . India has made clear that it believes last week 's coordinated attacks in Mumbai originated in Pakistan , but the Indian government is under pressure to explain the lapse of security that allowed the siege to occur . Indian police say 179 people were killed in the attacks on 10 targets in Mumbai . Most of the deaths occurred at the city 's top two hotels , the Oberoi and the Taj Mahal . Watch report about nanny saving infant . Pakistani authorities say Islamabad has not received any evidence that militants from within its borders carried out the attacks , but have vowed to fully cooperate in the investigation . Suspicion has fallen on Lashkar-e-Tayyiba , a Pakistan-based terror group allied with al Qaeda , even though it has denied responsibility . Watch how attacks could damage relations » . Pakistan banned the group in 2002 after an attack on India 's parliament that brought the two countries to the brink of war . Indian security forces say they arrested a member of the group in February , noting that the man was casing Mumbai for an attack . U.S. counterterrorism officials continue to say signs are pointing to Lashkar-e-Tayyiba and they have n't seen anything to rule it out . However , they will not definitively say the group is responsible . A team of FBI agents is in Mumbai to assist in the investigation , and U.S. Secretary of State Condoleezza Rice is heading to New Delhi on Wednesday to try to ease strained relations between the nuclear neighbors . Watch Pakistan 's PM say his country will defuse tensions » . At the center of India 's investigation is the lone suspect in police custody , who Indian authorities say is Pakistani and trained by Lashkar-e-Tayyiba . Indian officials have identified the suspect as a clean-shaven young man who was photographed during the attack on Mumbai 's Victoria Terminus train station . One of the still images shows him walking with one arm outstretched and a gun in his other hand , lowered by his side . He is wearing a black T-shirt , cargo pants and a backpack . Watch Anderson Cooper talk with Fareed Zakaria about the attacks » . Indian police say the other nine attackers were killed in three days of battles with police and the Indian military . CNN 's Senior International Correspondent Nic Robertson contributed to this report .
U.S. warned Pakistan about potential Mumbai attacks , source says . Violence that killed innocent people have strained India - Pakistan relations . Suspect is from Pakistan , Indian authorities say . Pakistan PM rejects claims his country had role in the massacre .