Flight QZ8501 went down on December 28 in stormy weather during a short trip from the Indonesian city of Surabaya to Singapore, with 162 people on board.
After a lengthy search often hampered by bad weather, a Singapore military vessel spotted the fuselage, the plane's main body, believed to be the resting place of most of the victims, at the bottom of the Java Sea on Wednesday.
An advance team of 15 divers plunged into the water early Thursday to examine the main portion of the jet, Mr S.B. Supriyadi, a rescue agency official coordinating the search, told AFP.
"They will first assess how many bodies are still trapped inside the fuselage," he said. "Hopefully we can retrieve all the victims as soon as possible."
Just 50 bodies have so far been recovered.
National search and rescue chief Mr Bambang Soelistyo previously said that if divers had problems retrieving bodies from the wreckage while it is still on the seabed, officials would try to lift it.
The fuselage is attached to part of a wing, and the wreckage is 26 metres (85 feet) long.
Rescuers have already used giant balloons to lift the plane's tail out of the water, after it was found about two kilometres (1.2 miles) from the main body.
The discovery of the fuselage followed the retrieval earlier this week of the jet's black boxes, the flight data recorder and cockpit voice recorder, which contain crucial information that should help determine why the plane went down.
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