Moscow, December 29 (RHC)-- Russian investigators looking into the crash of a military plane that crashed, killing all 92 on board, believe a fault with its wing flaps was the reason it plunged into the Black Sea, an investigative source told the Interfax news agency.

The plane, a Tupolev-154 belonging to the Defense Ministry, disappeared from radar screens two minutes after taking off on Sunday from Sochi in southern Russia, killing dozens of Red Army Choir singers and dancers en route to Syria to entertain Russian troops in the run-up to the New Year.

The three black box flight recorders from the aircraft were found on Tuesday, Russian news agencies said, amid unconfirmed reports that authorities had grounded all aircraft of the same type.  The Defense Ministry confirmed one box had been found.

The Life.ru news portal, which has close contacts to law enforcement agencies, said it had obtained a readout of one of the pilot's last words, indicating a problem with the wing flaps: "Commander, we are going down," the pilot was reported to have said.  There was no official confirmation of the readout.

The Defense Ministry said search and rescue teams had so far recovered 12 bodies and 156 body fragments.