Authorities said Wednesday they believed they had pinpointed the resting place of the Lion Air jetliner, which vanished from radar screens after taking off on a flight to nearby Bangka-Belitung island.
"We dug and we got the black box", a diver, identified as Hendra, told broadcaster Metro TV on board a search vessel, the Baruna Jaya, describing how his team found the orange-colored box intact in debris on the muddy sea floor.
Data from the doomed flight shows the plane was struggling with erratic speed and altitude levels during the brief time it was in the sky.
Yusuf Latif, a spokesman for Indonesia's search and rescue agency, stopped short of confirming that a black box had been found, but confirmed the finding of "an orange object".
Although it is now nearly certain that everyone on the plane died, relatives are desperate to find traces of their loved ones.
There is no ban or suspension of Lion Air flight operations in Malaysia following a crash involving the airline's aircraft in Indonesia on Monday, Transport Minister Anthony Loke Siew Fook said.
Didi Hamzar, director of preparedness with Indonesian Search and Rescue Agency (Basarnas) said at a press conference that an object was found which was likely to be a large part of the cabin of the missing plane, Efe news reported.
The search is now planned to last seven days and could be extended, the report added.
It has also suspended Lion Air's technical director and several technicians who cleared the plane to fly.
Passengers on the Sunday flight from Bali to Jakarta have recounted problems that including a long-delayed take-off for an engine check and terrifying descents in the first 10 minutes in the air.
At one point, the passenger who shot the video, Paul Ferdinand Ayorbaba, zoomed in on the flight number on his boarding pass. He is seen walking along a concourse, showing his Lion Air boarding pass on camera, and zooming in on a Lion Air aircraft while boarding, according to AP.
Indonesia's Transport Ministry said the Boeing 737-800 plane, which took off from Jakarta about 6.20 a.m., crashed just 13 minutes later. This saw Indonesian airlines temporarily banned from flying to European countries.