Indonesia plane crash investigators hunt for black boxes buried in seabed mud

Authorities believe 737-500 jet broke up on impact with sea rather than in mid-air

Divers searching for the black boxes of a crashed Sriwijaya Air jet in Indonesia are using a high-tech “ping locator” equipment to look for an identified target beneath 20 metres of seabed mud.

Signals from the plane’s cockpit voice and flight data recorders were detected between Lancang and Laki islands in the Thousand Island chain just north of Jakarta's coast, officials said.

The Boeing 737-500 jet carrying 62 people nosedived at high speed into the Java Sea on Saturday.

The aircraft disappeared minutes after taking off from Jakarta during heavy rain. Investigators believe the jet broke up on impact with the sea rather than in mid-air.

Plane parts and human remains have been recovered but there has not been any sign of survivors.

More than a dozen helicopters, 53 navy ships and 20 boats, and 2,600 rescue personnel have been searching the area since Sunday.

Landing gear, wheels and a jet engine were among the parts found, while other rescuers brought a dozen body bags containing human remains to a police hospital in eastern Jakarta to be identified.

Indonesia’s National Search and Rescue Agency tweeted on Monday that it had found more body parts and aircraft debris.

Ridwan Bae, a member of the Indonesian parliament, who was at the scene of the investigation, expressed his concern about the conditions of commercial aviation in Indonesia and said he would raise the issue with the transport minister.

Once the recording devices are found and taken to the investigators' facility, it will take up to five days to dry and clean them and to download the data.

A search operation is ongoing in the Java Sea after the jet crashed minutes after takeoff on 9 January (AFP via Getty Images)

National Transportation Safety Committee investigator Nurcahyo Utomo said recordings and transcripts of the conversation between the pilot and air traffic controllers had been collected as part ofthe probe into the cause of the crash.

He added his his team was examining radar data on the plane's movements and interviewing the air traffic officers who were in charge of controlling the crashed flight. 

More interviews of witnesses, including with the airlines' technicians, fishermen and experts, will be done in the near future.

Parts of the plane recovered from the seafloor include the ground proximity warning system, a radio altimeter which gives precise data on how close an aircraft is to earth’s surface, and several fragments from the lower side of the aircraft's tail.

Additional reporting by Associated Press