Surabaya , Indonesia ( CNN ) Divers are preparing to investigate underwater pings that may be coming from the flight recorders of AirAsia Flight QZ8501 , Indonesia 's military chief said Friday . An Indonesian search vessel had earlier detected the pings , said Gen. Moeldoko , the head of Indonesia 's armed forces . He was speaking on board the ship that is being used as a base for divers trying to raise the tail of the AirAsia plane , which went down in the Java Sea on December 28 with 162 people on board . But there is also caution surrounding the possible pings , because the sound could be emanating from other sources . In the case of Malaysia Airlines Flight MH370 , several signals raised hopes of locating the missing plane , but proved to be false leads . Search teams , which had been battling bad weather and strong currents , found the tail section on the sea floor Wednesday . That discovery was seen as significant because in the Airbus A320-200 , the aircraft model of Flight QZ8501 , the flight data recorder and cockpit voice recorder are housed in the tail . But before Friday , searchers had n't reported detecting any possible pings from the locator beacons on the flight recorders , which are popularly known as black boxes . It was unclear whether the devices remained inside the tail or had come free . Batteries that send out the pings last 30 days . It has been 13 days since the AirAsia plane fell into the sea . Conditions cleared up Friday , as divers prepared for a complicated operation to raise the tail to find the recorders . Divers are lowering ropes and slings down to the tail . The plan is to inflate giant airbags or balloons underneath to lift the tail from the bottom of the sea . A crane would then be used to raise the section . Search officials said that the underwater visibility and currents are much better than conditions in previous days . Experts say the information contained within the flight recorders is likely to enable investigators to figure out why Flight QZ8501 dropped off radar and went down in the sea on its way from the Indonesian city of Surabaya to Singapore . The plane 's pilot had asked to change course and climb to a higher altitude minutes before contact was lost , according to Indonesian officials . The vast majority of the people on the plane were Indonesian . There were also citizens of Great Britain , France , Malaysia , Singapore and South Korea . A total of 48 bodies have so far been recovered from the sea , Indonesia 's search and rescue agency said Friday . Some of the bodies have been found still strapped into seats . CNN 's Brad Olson , Madison Park and journalist Intan Hadidjah contributed to this report .
An Indonesian search vessel detected the pings , the country 's military chief says . The ship was carrying a Chinese cargo ship, which is believed to have been hijacked by pirates in recent days and taken into international waters off Somalia.