Lion Air flight JT610's black box

Members of a rescue team bring personal items and wreckage ashore at the port in Tanjung Priok, North Jakarta, after they were recovered from the sea where Lion Air flight JT 610 crashed off the north coast. (RESMI MALAU/AFP)

"We dug and we got the black box" from among debris in the mud on the sea floor, the diver, identified as Hendra, told broadcaster Metro TV on board the Baruna Jaya vessel.

The box was recovered at 10.15am in waters off Tanjung Karawang, West Java, by Indonesian divers, Kompas TV reported.

The black box was orange in colour and intact, the diver said, without specifying if it was the flight data recorder or the cockpit voice recorder.

There are two black boxes – the flight data recorder and the cockpit voice recorder. The digital flight data recorder gathers information about the speed, altitude and direction of the plane with enough storage for 25 hours of data, while the cockpit voice recorder keeps track of conversations and other sounds in the pilots' cabin.

The Boeing-737 MAX plane plunged into the Java Sea on Oct 29, just 13 minutes after taking off from Jakarta. It was headed to Pangkal Pinang city on Bangka island, an hour's flight away.

Rescue officials had been focused on recovering the main part of the aircraft – more specifically the plane’s black boxes – as investigators try to determine the cause of the crash.

As part of the search operation, Indonesian authorities deployed divers, search and rescue vessels, four sonar detectors and an underwater acoustic beacon.

Indonesia's National Transportation Safety Committee said 181 passengers – including two babies and one child – and eight crew members were on board.

Twenty employees from Indonesia’s Finance Ministry as well as Andrea Manfredi, an Italian former professional cyclist, were also among the passengers on the ill-fated flight.

Flight JT610 sped up as it suddenly lost altitude in the minutes before it disappeared, according to flight data tracking websites, with authorities saying witnesses saw the jet plunge into the water.

Indonesian officials named the captain of the flight as Bhavye Suneja, an Indian national who had been with the airline for seven years, local media reports said.

According to Lion Air, Suneja and his co-pilot, Harvino, had 11,000 hours of flying between them and had undergone medical checkups and drug testing recently.