Censor.NET reports citing RIA Novosti.
"A technical failure and a pilot error are considered as the major versions of the Tu-154 crash," RIA Novosti's source said.
Earlier, the Russian Defense Ministry's press-service reported that the Tu-154 disappeared from radars after taking off from the Adler airport.
84 passengers and eight crew members were on board. The plane was carrying military, nine reporters and musicians to participate in a New Year's performance for Russian troops deployed in Hmeymim airbase in Syria.
President of Russia Vladimir Putin was informed about the disappearance of the plane from the radars. Russian defense minister Sergei Shoigu held a meeting with the senior staff of the Armed Forces on the organization of search and rescue activities.
Fragments of the Tu-154 were found 1.5 km from Sochi coast at the depth of 50-70 meters, TASS reports citing the Russian Defense Ministry.
The press service of the Southern Regional Emergency Center has also confirmed the discovery of the plane crash site in the Black Sea. An oil spill was found 5.5 km from the coastline, and the aircraft fragments, in particular, the landing gear, were found 1.5 km from the coast. Body of one victim of the crash was found later six kilometers from Sochi coast.