PANGKALAN BUN, Indonesia -- Bad weather and poor underwater visibility on Thursday prevented Indonesian navy divers from searching inside the large chuck of AirAsia jet wreckage that is believed to be the fuselage.

At least 15 divers descended to the seabed at a depth of 28 metres to examine the piece of wreckage spotted Wednesday, calculate its weight and search for bodies. They were unable to do so because of the weather and sea conditions, 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. When bodies are found, the divers would try to put them in individual body bags, which rescuers on ships would then hoist to the surface, he said.

The 30-metre-long section of the plane body with a wing attached was sighted on the bottom of the Java Sea by a Singaporean navy ship.

Only 50 bodies have been recovered since the plane disappeared from radar and crashed in the sea Dec. 28 en route from Surabaya, Indonesia, to Singapore. Most of the 162 victims are Indonesian.

Rescuers believe that most of the bodies are inside the main fuselage.

Search and Rescue Agency chief Henry Bambang Soelistyo said the large piece of wreckage would be lifted from the seabed after the search for bodies was no longer considered effective.

The plane's flight data and cockpit flight recorders were retrieved earlier this week and will be key to learning the cause of crash. Bad weather is a suspected factor.

Nine aircraft and 10 ships conducted search operations Thursday. Two U.S. ships and one from Singapore have left, Soelistyo said.

The destroyer USS Sampson and combat ship USS Fort Worth left for other assignments after contributing more than 650 search hours for the AirAsia flight.

"The U.S. was extremely proud to assist" the search effort, U.S. Ambassador to Indonesia Robert O. Blake said. "We are all pleased with the recovery of the black boxes and location of portions of the plane that we hope will shed some light on the cause of this tragedy."