Russian investigators have determined that the flight recorders of the Kolavia Tupolev Tu-154 destroyed in a fire at Surgut contain records of the event.
The Interstate Aviation Committee (MAK) says that it has started analysing the information from the flight-data and cockpit-voice recorders.
It states that it is assessing the state of the aircraft's three Kuznetsov NK-8 engines, adding that all three were running at the time the blaze broke out on 1 January.
MAK says the weather conditions in Surgut, where temperatures have fallen to around minus 20°C, are "complicating" the inquiry. Investigators have constructed a heated tent over the wreckage.