The black box is a cockpit voice recorder and is one of two boxes crucial for the investigation. Deputy chief of Indonesia’s transport safety committee (KNKT) Haryo Satmiko said: “It’s been found, but we have not received information of the location yet.” The Boeing Co 737 MAX jet crashed into the sea on October 29 killing all 189 people on board.
Deputy maritime minister Ridwan Djamaluddin said the National Transportation Safety Committee had informed the ministry about the discovery.
He added human remains were also found at the seabed location.
The announcement comes just days after Lion Air ended its search for the second black box, forcing Indonesia to take over.
The first black box was found in the wreckage in November.
The flight recorder revealed there were problems with the air-speed indicator on four of the plane’s previous flights.
Indonesia Navy spokesman Agung Nugroho said the recorder was found 8m deep under mud on the sea floor.
The flight recorder data helped, but the voices of the pilots and ground control in the second black box could be key to piecing together exactly what happened.
The ill-fated flight, whose plane was only two months old, dived into the sea just minutes after taking off from the Indonesian capital.
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Flight JT610 had been on its way for the western city of Pankal Pinang.
The pilot had asked air traffic control for permission to turn back to the airport but then contact was lost.
It was the worst airline disaster in Indonesia since 1997, when 234 people died on a Garuda flight near Medan.
It was also the first-ever crash of a Boeing 737 MAX jet.
Lion Air is one of Indonesia’s youngest airlines, but has grown rapidly in recent years now flying to dozens of domestic and international destinations.