(CNN) A massive search and rescue operation is under way in the Black Sea after a Russian military plane crashed Sunday with 92 on board. Thirteen bodies have so far been recovered, as well as more than 150 pieces of debris, the Itar-Tass news agency reported, quoting a source in security agencies.

Terrorism was not a likely cause of the crash, Kremlin spokesman Dimitri Peskov said in a call with reporters Monday. Russia's transport minister said it was assumed the plane had crashed due to technical malfunction or pilot error.

The Tupolev Tu-154 plane carrying 84 passengers and eight crew crashed in the Black Sea near Sochi after disappearing from radar Sunday morning local time, state-run Ria Novosti news agency reported.

The Defense Ministry said there appeared to be no survivors. Russia is observing a national day of mourning Monday.

Photographs of Channel One, NTV and Zvezda TV journalists killed in the plane crash are seen outside the Ostankino Technical Center in Moscow.

Photographs of Channel One, NTV and Zvezda TV journalists killed in the plane crash are seen outside the Ostankino Technical Center in Moscow.

Two women stand outside Alexandrov Hall, a rehearsal room of the Alexandrov Ensemble, in Moscow on Sunday. The ensemble, established in 1928, has toured the world performing Russian folk songs, World War II anthems and patriotic music.

Two women stand outside Alexandrov Hall, a rehearsal room of the Alexandrov Ensemble, in Moscow on Sunday. The ensemble, established in 1928, has toured the world performing Russian folk songs, World War II anthems and patriotic music.

Flowers lay in front of a photo of the Alexandrov Ensemble at the group's building in Moscow. "These people always performed in war zones, they wore uniforms, they brought kindness and light," Kibovsky said.

Flowers lay in front of a photo of the Alexandrov Ensemble at the group's building in Moscow. "These people always performed in war zones, they wore uniforms, they brought kindness and light," Kibovsky said.

A man places flowers outside the building of the Alexandrov Ensemble in Moscow on Sunday. Alexander Kibovsky, head of Moscow's culture department, called them "our cultural paratroopers."

A man places flowers outside the building of the Alexandrov Ensemble in Moscow on Sunday. Alexander Kibovsky, head of Moscow's culture department, called them "our cultural paratroopers."

A man places a candle outside the building of the famed Alexandrov Ensemble, the Russian army's official dance and choir company, in Moscow.

A man places a candle outside the building of the famed Alexandrov Ensemble, the Russian army's official dance and choir company, in Moscow.

Russian police secure the area near where the plane crashed. In addition to the ensemble, the plane was carrying eight crew, eight soldiers and nine journalists.

Russian police secure the area near where the plane crashed. In addition to the ensemble, the plane was carrying eight crew, eight soldiers and nine journalists.

Russian President Vladimir Putin, left, and Nursultan Nazarbayev, president of Kazakhstan, speak to members of the media in St. Petersburg, Russia, on December 25. Putin has ordered Prime Minister Dmitry Medvedev to lead an investigation of the crash, Russian news agency Sputnik reported.

Russian President Vladimir Putin, left, and Nursultan Nazarbayev, president of Kazakhstan, speak to members of the media in St. Petersburg, Russia, on December 25. Putin has ordered Prime Minister Dmitry Medvedev to lead an investigation of the crash, Russian news agency Sputnik reported.

Russian emergency workers carry remains from the wreckage of the Tu-154 plane that crashed near Sochi on December 25.

Russian emergency workers carry remains from the wreckage of the Tu-154 plane that crashed near Sochi on December 25.

Russian emergency personnel work near the site of the crash on December 25. The plane was en route from Moscow to Syria and had stopped in Sochi to refuel.

Russian emergency personnel work near the site of the crash on December 25. The plane was en route from Moscow to Syria and had stopped in Sochi to refuel.

People hold a candlelight vigil for victims of the crash on Sunday, December 25, in Sochi.

People hold a candlelight vigil for victims of the crash on Sunday, December 25, in Sochi.

A Russian police orchestra musician places a flower in tribute to members of the Alexandrov Ensemble outside their home stage building in Moscow on December 26. The popular ensemble was scheduled to perform for Russian pilots in Syria ahead of New Year's Day.

A Russian police orchestra musician places a flower in tribute to members of the Alexandrov Ensemble outside their home stage building in Moscow on December 26. The popular ensemble was scheduled to perform for Russian pilots in Syria ahead of New Year's Day.

People visit a makeshift memorial to victims of the crash at a pier in Sochi on December 26. Russia is observing a national day of mourning for the eight crew and 84 passengers aboard.

People visit a makeshift memorial to victims of the crash at a pier in Sochi on December 26. Russia is observing a national day of mourning for the eight crew and 84 passengers aboard.

Wreckage from the Tu-154 plane is hauled from the Black Sea late on Monday, December 26.

Wreckage from the Tu-154 plane is hauled from the Black Sea late on Monday, December 26.

A woman lights a candle Tuesday next to makeshift memorial in Sochi, Russia, for Russian activist Elizaveta Glinka, who was killed in the crash. Also presumed dead were nine journalists and more than 60 members of the Russian army's official choir, the Alexandrov Ensemble.

A woman lights a candle Tuesday next to makeshift memorial in Sochi, Russia, for Russian activist Elizaveta Glinka, who was killed in the crash. Also presumed dead were nine journalists and more than 60 members of the Russian army's official choir, the Alexandrov Ensemble.

Emergency Ministry personnel prepare a submersible craft Tuesday to search for sunken wreckage and victims' remains. Thirteen bodies had been recovered from the Black Sea as of Tuesday morning.

Emergency Ministry personnel prepare a submersible craft Tuesday to search for sunken wreckage and victims' remains. Thirteen bodies had been recovered from the Black Sea as of Tuesday morning.

On Tuesday, December 27, members of Russia's Emergency Ministry pack a flight recorder recovered from a Russian military plane that crashed Sunday into the Black Sea with 92 people aboard. Russia's transport minister said it was assumed the plane had crashed due to technical malfunction or pilot error -- not terrorism.

On Tuesday, December 27, members of Russia's Emergency Ministry pack a flight recorder recovered from a Russian military plane that crashed Sunday into the Black Sea with 92 people aboard. Russia's transport minister said it was assumed the plane had crashed due to technical malfunction or pilot error -- not terrorism.

The ministry said 3,500 search and rescue personnel are involved in the search.

Searchers have not paused "for a minute during the night," the ministry said Monday. "Experts thoroughly analyzed control data from radio-location equipment and determined the Tu-154's flight trajectory."

Ships, divers and aircraft continue to arrive in the search area. The search-and-rescue operation has 39 ships and cutters, 135 divers and 7 deep-water vehicles.

"Military personnel of the Southern Military district keep examining the shoreline to find and collect the bodies, debris of the plane and personal belongings of passengers," it said.

Divers found the Tu-154's fuselage about a mile offshore in the Black Sea at the depth of 27 meters, RIA Novosti reported.

Earlier Monday a military plane flew 10 bodies and fragments of debris to Moscow, where DNA testing would be carried out, the ministry said.

It said experts had been able to more precisely locate the crash site by using data from radio location equipment, but that the search was complicated by varying sea depths.

The Tupolev plane was carrying members of the army's official choir -- the Alexandrov Ensemble --"flying to congratulate Russian air force pilots in Syria with the New Year," Defense Ministry spokesman Igor Konashekov said Sunday.

The plane took off from Moscow and was headed to the Russian Hmeymim airbase in Latakia, Syria, where Russia has a large military presence, a source told Russia's state news agency Tass.

En route to Syria, the plane landed in Sochi to refuel, the Defense Ministry's press service told Russia's Interfax news agency.

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Why the plane crashed is not yet known.

Russian President Vladimir Putin has ordered Russia's Prime Minister Dmitry Medvedev to lead an investigation, according to Russian news agency Sputnik.

Russian Transport Minister Maxim Sokolov said Monday that "the major versions do not include the terrorist attack, so we assume that the cause of the crash could be either technical malfunction or pilot error," according to state-run TASS.

It quoted Viktor Ozerov, chairman of the Federation Council Committee on Defense and Security, as saying he completely ruled out terrorism.

"I rule out version of the terror attack completely. It is the aircraft of the Ministry of Defense, the airspace of the Russian Federation, there cannot be such a version," Ozerov is quoted as saying. "The plane had to make a U-turn after takeoff over the sea (and) may (have taken) the wrong direction."

Russian Transport Minister Maxim Sokolov said Monday that "the major versions do not include the terrorist attack, so we assume that the cause of the crash could be either technical malfunction or pilot error," according to TASS.

The Russian Investigation Committee has launched a routine criminal investigation to examine potential "violation of rules of flight safety or preparation," committee spokesperson Svetlana Petrenko earlier told Tass. The committee plans to seize documents and interrogate those who prepared the plane for flight, she added.

CNN Meteorologist Derek Van Dam said no major weather patterns were present at the time of the plane's disappearance.

The victims

According to a Defense Ministry list, among those on board were eight crew members, eight soldiers and more than 60 members of the Alexandrov Ensemble, including its conductor Valery Kahlilov.

A photo of a Tupolev Tu-154, the same plane that disappeared Sunday morning after taking off near Sochi, Russia.

Since 1928, the Alexandrov Ensemble has grown into a immensely popular tradition due to its unending government support. It has toured the world performing Russian folk songs, World War II anthems and patriotic music, and was dubbed "Russia's singing weapon."

Tass is reporting that at least 12 family members have arrived in Sochi and the rector of the St. Nicolas Church in Sochi, archpriest Dmitry Petukhov, has conducted a service in memory of the flight's victims at an airport chapel.

Another passenger was the famous Russian human rights activist, Liza Glinka, according to CNN affiliate RBC. She was bringing medicine and other supplies to a local hospital in Syria, her colleague and friend Dr. Sergey Kurkov told RBC.

A Facebook page for Glinka's charity "Fair Aid" carried a post mourning "this huge loss for our entire nation."

Nine journalists, including three reporters with Star TV, were also on board, the Defense Ministry said on its television network.