At least 41 people died after a passenger plane made an emergency landing in Moscow on Sunday, with flames coming from its fuselage.
Passengers leapt on to an inflatable slide at the front and ran from the blazing plane as huge black columns of smoke billowed into the sky.
"There were 78 people including crew members on board the plane," the Investigative Committee said.
The committee said the flight was headed to the north-west Russian city of Murmansk.
"According to the updated info the investigation has as of now, 37 people survived."
Health Minister Veronika Skvortsova said later that 38 survived, implying the death toll was 40.
Black smoke and flames rose above the plane's tail after it had made an emergency landing in Moscow's Sheremetyevo airport.
Witness Alyona Osokina said she was inside the terminal when she suddenly saw a plane on fire rushing along the runway.
"The blaze was devouring the plane," she told Rain TV.
Ms Osokina said fire engines had arrived quickly but could not immediately put out the blaze.
Emergency services appeared to have extinguished the flames but smoke was still visible in photos circulating on Twitter.
"This horror and tragedy happened before our eyes," she said, adding that those who managed to flee the plane then walked towards the airport.
"I believe they were in a state of deep shock."
The plane, a Russian-made Superjet 100, had just taken off from Sheremetyevo on a domestic route when the crew issued a distress signal, officials said.
"After the take-off, the crew reported an anomaly and decided to come back to the departure airport. At 6.30 pm, the aircraft made an emergency landing," the airport said in a statement.
Aeroflot, Russia's flagship airline, said the plane had to return to the airport "due to a technical reason" and its engines caught fire upon landing. Previous reports had said the fire broke out in mid-air.
One passenger said the plane had been hit by lightning, a Russian news outlet reported.
"Flight SU-1492 took off on schedule at 6.02pm," the airport said.
"After the take-off, the crew reported an anomaly and decided to come back to the departure airport. At 6.30pm, the aircraft made an emergency landing."
The plane is largely used in Russia as a replacement for outdated Soviet-era aircraft, but also has been used by airlines in other countries, including Armenia and Mexico.
This is the second fatal accident involving a SSJ100. In 2012, a demonstration flight in Indonesia struck a mountain, killing all 45 aboard
