Indonesian navy divers were trying to find and retrieve bodies Thursday believed to be trapped inside a large chunk of the AirAsia jet's fuselage, an official said.

Indonesian Search and Rescue Agency chief Henry Bambang Soelistyo said the fuselage, which was spotted Wednesday by a Singaporean navy ship, would be lifted from the seabed after the search for bodies was no longer considered effective.

The 30-meter-long (100-foot-long) section of the plane body with a wing attached was sighted on the bottom of the Java Sea. Rescuers believe that most of the bodies of the 162 people on board are inside.

So far, only 50 bodies have been recovered from the Dec. 28 crash less than halfway into a two-hour flight from Surabaya, Indonesia, to Singapore. Most of the victims are Indonesian.

At least 15 divers descended to the seabed at a depth of 28 meters (92 feet) to examine wreckage, calculate its weight and search for the bodies. When corpses are found, the divers will try to put them in individual body bags, which rescuers on ships will then hoist to the surface, said Suryadi Bambang Supriyadi, the operation director at the National Search and Rescue Agency.

He said it appeared that some parts of the fuselage have been covered with silt.

The plane's "black boxes"_- the flight data and cockpit flight recorders — were retrieved on Monday and Tuesday. They will be key to learning what caused the plane to crash. Bad weather is a suspected factor.

Nine aircraft and 10 ships including one from China were involving the search operation Thursday. Two U.S. ships and one from Singapore have left the mission area, Soelityo said.