Russian investigators have discovered evidence of an electrical fault on the burned-out Tupolev Tu-154 at Surgut, which showed up the day before fire destroyed the jet.
The Russian Interstate Aviation Committee (MAK) turned up the evidence during a preliminary analysis of information on the flight-data recorder of the Kolavia aircraft.
Three occupants on the jet were killed in the fire which, says MAK, began in the rear fuselage as it prepared to taxi on 1 January.
On the day before the accident there was an indication "testifying to the malfunction of the power supply system", it states.
MAK is convening a specialist working group to analyse technical aspects of the Tu-154's electrical supply.
It states that it is trying to examine the remains of power-supply circuitry in the rear structure of the aircraft, but says the electrical equipment has been "severely damaged" by the fire.