Speed sensors that were iced over may have caused the passenger jet crash near Moscow that killed 71 people, investigators say.
The Saratov Airlines jet went down minutes after take-off from Moscow's Domodedovo airport on Sunday.
The Antonov An-148 was heading to Orsk in the Ural mountains and lost contact at 2.27pm local time on Sunday.
A preliminary analysis of the on-board flight recorder indicated the plane had problems two and a half minutes after it took off, at an altitude of about 4265 feet.
The country's Interstate Aviation Committee said instruments began displaying different speed readings, probably because of iced speed sensors while their heating systems were shut off.
Russia's Investigative Committee said the plane was intact when it crashed and that the explosion happened on impact. It crashed near the village of Argunovo, about 80km south-east of Moscow. It did not send any emergency call.
The emergencies ministry is collecting DNA samples from victims' relatives as part of the identification process of the 65 passengers, including a child and two teenagers, and six crew.
When the crew detected the issue, they switched off the plane's autopilot. They eventually took the plane into a dive at 30-35 degrees.
The jet, which was reportedly seven years old, was being flown by an experienced pilot who had 5000 hours of flying time.
Russian media reports said the plane's captain had rejected a de-icing treatment on the plane before takeoff. The procedure is optional and the crew's decision is based mainly on the weather conditions.
A criminal inquiry has been launched.
A previous crash in 2009 of an Air France plane, killing 228 people, was also thought to have been caused by iced-over speed sensors.
More than 1400 body parts and hundreds of plane fragments have been recovered from the crash site.
Wreckage is strewn over a large area - about 30 hectares - and more than 700 people were involved in the search operation, struggling through deep snow.