A Russian plane crash that killed 71 people may have been caused by incorrect information being displayed about the aircraft's speed.
Investigators have said ice on speed-measuring instruments - and the pilots' failure to turn on heating systems that would have thawed the frozen sensors - led to the flawed speed data that preceded the crash.
Russian newspaper RBK cited sources who said the captain of the flight refused a de-icing procedure at the airport - a decision the Komersant newspaper previously said was optional in the mild temperature conditions that day.
"A factor in the development of a special situation in the flight could be the wrong data about flight speed on pilots' indicators which was likely due to iced pitot tubes (speed probes) while their heating systems were shut off," the Russian Interstate Aviation Committee said.
Everyone aboard the plane was killed when the plane plunged into a snowy field about 65 kilometres from Moscow's Domodedovo airport, six minutes after taking off.
The IAC, which investigates aircraft incidents, suggested the cause of the crash after studying the plane's flight data recorder, which showed that the pilots saw varying data on two air speed indicators.
It said it will continue its investigation by examining the flight's black box, which records conversations in the cockpit.
The plane had been in autopilot after takeoff, investigators said, but pilots took back manual controls when they saw the varying data.
The plane dropped 40 metres per second in its final moments, according to the flight tracker.
Russian authorities have been combing through snow at the crash site, where they say they have recovered 1,400 body parts and 900 plane fragments.
Domestic carrier Saratov Airlines, which operated the An-148 flight, has said it will suspend usage of the type of plane involved.
Iced pitot tubes were named as the likely reason for the Air France 447 crash, which killed 228 people when the plane plunged into the Atlantic in 2009.