Speed sensors that were iced over may have caused a passenger jet to crash near Moscow, killing all 71 people on board, investigators say.
The faulty instruments could have given the pilots wrong speed data, Russia’s Interstate Aviation Committee said.
The Saratov Airlines jet went down minutes after take-off from Moscow’s Domodedovo airport on Sunday.
No emergency call came from the plane. The Antonov An-148 was en route to Orsk in the Ural mountains.
What are the investigators saying?
A preliminary analysis of the flight recorder indicated problems two and a half minutes after the plane took off, at an altitude of around 1,300m (4,265ft), the committee said.
At that moment, the instruments began displaying different speed readings. The pilots turned off the autopilot and the plane began to lose speed until it crashed.
What do we know so far?
Contact was lost at 14:27 (11:27 GMT), minutes after the plane took off.
The plane crashed near the village of Argunovo, about 80km (50 miles) south-east of Moscow.
Russia’s Investigative Committee said the plane was intact when it crashed and that the explosion happened on impact. Flight-tracking site Flightradar24 said it then descended at the rate of 1,000m (3,300ft) per minute.
Wreckage and body parts are strewn over a large area – about 30 hectares (74 acres) – and more than 700 people are involved in the search operation, struggling through deep snow.
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.
The jet, which was reportedly seven years old, was being flown by an experienced pilot who had 5,000 hours of flying time.