Russian divers were able to recover the second black box on Wednesday from a military plane that crashed into the Black Sea. The Defense Ministry also announced that it had been able to recover 15 bodies from the site, as well as some remains of other victims.

The TU-154 Soviet-era aircraft floundered on Sunday, shortly after a refueling stop in Sochi. The tragedy killed all 92 people onboard, including some 60 members of the renowned Alexandrov Ensemble, who were scheduled to perform for Russian troops at a military base in Syria.

Some 3,600 people were involved in the massive recovery effort, employing the help of around 200 navy divers as well as drones and submersibles. Russia's FSB security agency has indicated it is investigating four likely reasons for the crash: technical faults, pilot error, bad fuel or the presence of a foreign object in the plane's engine.

Authorities have said that their preliminary findings make an act of terrorism appear unlikely, but that it had not been completely ruled out.

Media: Faulty flaps caused crash

Two Russian news outlets, the "Komsomolskaya Pravda" newspaper and Life.ru, wrote that they had obtained a transcript of the cockpit conversation recorded in the first black box, which was recovered Tuesday. According to both, a pilot can be heard yelling about an issue with the aircraft's flaps before shouting "Commander, we are falling!"

The report is unverified, but both sources were known to have long-standing connections with the Kremlin. The "Kommersant" daily also reported that investigators were focusing on the theory that faulty flaps compounded by pilot error caused the crash.

The TU-154 has long been retired by commercial airlines, but it has enjoyed continued use by military and government agencies. It has been involved in a number of fatal crashes, including an April 2010 disaster that claimed the life of the (then) Polish president- President Lech Kaczynski- and 95 others. In the wake of Sunday's crash, Russia has grounded all TU-154 aircraft until the cause of Sunday's crash can be determined.

es/sms (AFP, AP)