Russian investigators at the scene of a deadly plane crash near Moscow said on Sunday they were exploring all possible causes.
Among them are weather conditions, human error and the plane's technical condition.
The passenger plane crashed near Moscow soon after take-off on Sunday, killing all 71 people on board, authorities said.
No distress signals had been received from the crew.
Temperatures were around minus 5 degrees Celsius when the short-haul AN-148 operated by Saratov Airlines took off for the city of Orsk near the border with Kazakhstan, about 1,500 km southeast of the capital.
It reportedly disappeared from radar screens just minutes after taking off from Moscow's Domodedovo airport.
A spokeswoman for Saratov Airlines said there had been no concerns about the state of the plane, which was manufactured in 2010 and went into service with the airline in 2016.
The plane was carrying 65 passengers and six crew. Investigators said debris and human remains were spread over a radius of one kilometre from the crash site.
TV images of the crash site showed wreckage of the plane, including at least one engine, lying in fields covered with snow.
Helicopters were at the scene as well as rescuers on snowmobiles. An official of the Emergency Situations Ministry said two bodies and a flight recorder had been found.
Interfax news agency said one Swiss national had been among the passengers.
President Vladimir Putin offered condolences to those who had lost relatives and ordered a special investigative commission to be set up to probe the crash.
Local media website Ural56.ru in the Orenburg region showed footage of distressed relatives at Orsk airport. The city's mayor told the Rossiya 24 TV channel a team of psychologists had been deployed there to comfort them.