Initial information from the scene of the fatal Kolavia Tupolev Tu-154 fire in Surgut points to an electrical problem as the source of the blaze.
Russia's emergency situations ministry states that three people on board the aircraft were killed in the 1 January fire.
It adds that, as the engines on the Tu-154 were started, the fire developed "as a result of a short-circuit in on-board electrical equipment".
Video images of the accident indicate a strong fire in the central fuselage section, with flames erupting from the exits over the wings, as well as from the right-hand side, just ahead of the starboard engine, where a rear exit is located.
The airline and the emergencies ministry are putting the total number of occupants at around 135, including 116 passengers, eight crew and up to 11 employees of the carrier.
Investigators have retrieved both the cockpit-voice and flight-data recorders from the wreckage, says the Russian Interstate Aviation Committee (MAK) which will head the inquiry.
MAK says that it has started work on inspecting the structural components of the aircraft and its engines. It has neither confirmed the nature of the fire nor the circumstances which led to the blaze, which completely destroyed the tri-jet.
Kolavia flight 7K348 had been scheduled to operate from Surgut to Moscow Domodedovo when the fire broke out at around 15:00.