Russian authorities said that search teams have found the main "black box" flight data recorder from a military passenger jet that crashed in the Black Sea en route to Syria, and that it is too early to say what caused the disaster.
The Defense Ministry said on December 27 that the black box appears to be in good condition and was sent to the Air Force Central Research Center in the Moscow region for decoding, Interfax reported.
The ministry said the black box was found some 1,600 meters from shore off the Russian coastal city of Sochi.
The Defense Ministry Tupolev Tu-154 airplane -- which was carrying more than 60 members of the official military choir, the Aleksandrov Ensemble -- crashed on December 25 a few minutes after taking off from Sochi.
All 92 passengers and crew on board the plane died in the crash.
Officials said on December 27 that they have found 12 bodies and more than 150 body parts in their search of the wreckage of the plane.
Some reports said the second black box had been located along with several pieces of the fuselage.
"The debris is at the depth of 27 meters, one kilometer from the shore," said Rimma Chernova, a spokeswoman for the Sochi-based search-and-rescue operations run by Russia's Emergency Situations Ministry.
Transport Minister Maksim Sokolov said specialsts would begin examining the data recorder on December 27, and cautioned that it was still "premature to draw conclusions" about the cause of the crash.
"I said this yesterday, and not just me but others as well, including the FSB: the theory of a terrorist act is not considered the main theory of the cause of this plane crash," Sokolov said, referring to the Federal Security Service -- Russia's main domestic intelligence agency.
He said the plane had broken into several pieces when it crashed, and that there might not be one single large, intact piece of the fuselage among the wreckage.
"We are seeing several localized zones where fragments are being found," Sokolov said.
The massive search operation involves several ships, divers, and submersible drones covering some 10.5 square kilometers.
"We are doing everything to search for the bodies and investigate the causes of this awful tragedy," Defense Minister Sergei Shoigu said at a meeting in the Defense Ministry on December 27.
The FSB said there have thus far been "no signs or facts pointing to a possible act of terror" as the cause of the crash.
Eyewitness Video, 'Cockpit Conversation'
According to Russian media, the FSB says possible causes of the crash include pilot error, a technical problem, a foreign object getting caught in an engine, or poor-quality fuel.
New eye witnesses of the Russian Defense Ministry’s Tu-124 plane crash have been found and questioned, Investigative Committee Spokesperson Svetlana Petrenko told TASS on December 27.
“One of the witnesses made a video of the plane taking off and crashing into the sea," she said.
"Apart from this video, the video of the Tu-154 plane landing at the Sochi airport as well as videos showing the plane taxiing toward the parking stand and its passengers going through passport control, were also retrieved by investigators,” she added.
The website Life.ru published what it described as the transcript of a cockpit conversation, with one pilot yelling about a problem with the plane’s flaps and then shouting: "Commander, we’re falling!"
RFE/RL could not verify the report by Life.ru known to have good connections with Russian security agencies.
Other reports suggested the black box that was retrieved first was a data recorder, not a voice recorder.
The world-famous Aleksandrov Ensemble was on its way to entertain Russian troops stationed at the Hmeimim air base near the Syrian coastal city of Latakia for New Year's.
Nine Russian TV journalists were on the plane, as was humanitarian activist Yelizaveta Glinka, also known as Dr. Liza, a prominent member of President Vladimir Putin's advisory human rights council and executive director of the Spravedlivaya Pomoshch (Fair Aid) charity fund.
Russia has backed Syrian President Bashar al-Assad throughout the nearly six-year civil war in Syria and has been carrying out air strikes targeting rebels fighting against Assad's forces since September 2015.
In October 2015, a Russian airliner carrying more than 200 tourists from the Egyptian resort of Sharm el-Sheikh blew up over Egypt en route to St. Petersburg. An affiliate of the Islamic State extremist group claimed to have caused the downing of the plane in retaliation for Russia's military actions in Syria.
The military flight carrying the Aleksandrov Ensemble originated in Moscow and made a stopover in Sochi to refuel. It disappeared from radar two minutes after taking off.
Russia held a national day of mourning on December 26 in Moscow. Mourners laid flowers and lit candles in front of a concert hall where the ensemble often performed.
Deputy Defense Minister Nikolai Pankov said in Moscow early on December 26 that "the ensemble will live" and that it "will continue to remain a symbol of the army and our country."
With the total staff and membership of the musical ensemble numbering 285 people, Pankov said "the losses are very large."
He said Russia's military "will be working very seriously to make up these losses."
According to the Defense Ministry, the aircraft had been flown some 7,000 hours since it went into service in 1983.
The plane last underwent repairs in December 2014 and was serviced in September, the ministry said.
Russia's Investigative Committee said a criminal probe had been launched to determine whether violations of air-transport safety regulations had led to the crash.
Investigators were questioning the technical personnel responsible for preparing the plane for takeoff, the committee said.
Interfax reported on December 27 that the Defense Ministry and Russian security agencies have suspended all flights of the Tupolev Tu-154 planes until the reasons for the crash of the plane near Sochi are discovered.
Russian officials released a satellite image of the area near Sochi shortly after the crash.