Experts are examining three possible causes for a passenger plane disaster in Russia as passengers claimed a lightning strike forced the doomed aircraft to turn around.
Both flight recorders have been recovered from the Aeroflot SSJ100, which erupted into a ball of flames as it came down hard on the runway at Moscow's Sheremetyevo Airport on Sunday.
Forty-one people died after the aircraft caught fire during the emergency landing.
New footage on Monday showed investigators examining the burned out exterior and interior of the wreckage.
What have officials said about the lightning strike claim?
Video report by ITV News Correspondent Juliet Bremner
Investigators have not commented on the lightning strike claim, which emerged from those on board.
"We took off and then lightning struck the plane,” passenger Pyotr Egorov told the Komsomolskaya Pravda newspaper.
"The plane turned back and there was a hard landing. We were so scared, we almost lost consciousness.
"The plane jumped down the landing strip like a grasshopper and then caught fire on the ground."
What are investigators' three possible theories for the crash?
Russian investigators identified the three possible causes as: inexperienced pilots, equipment failure and bad weather.
Storms were passing through the Moscow area at the time of the crash.
The reason why the pilots decided to make an emergency landing has not been announced.
What is known so far about the crash?
The plane, which was carrying 73 passengers and five crew members to Murmansk, turned back for a still-unknown reason to Sheremetyevo Airport on Sunday evening.
The doomed landing occurred at 6.30pm, about a half hour after takeoff, suggesting the plane had little time to dump its fuel on return.
Witnesses captured the fire sparking towards the back of the Superjet and plumes of black smoke trailing the plane as it skidded across the runway.
Video on Russian news channel Rossiya-24 showed passengers hurtling down emergency slides towards the front of the plane while the fire raged at the back and middle of the plane.
What is known about the deaths?
Forty-one of the 78 people on board died, including two children. All bodies have been recovered from the plane.
Six survivors were taken to hospital.
Flight attendant Maxim Moiseev was confirmed among the dead.
Russian news reports, citing unnamed sources, said he was in the back part of the plane and had tried in vain to deploy an evacuation slide.
What else is known about the investigation?
Russia's main investigative body confirmed on Monday both of the plane's flight recorders - data and voice - have been recovered.
"Investigators soon will begin interviewing victims, eyewitnesses, airport staff and the airline carrier, as well as other persons responsible for the operation of the aircraft," Investigative Committee spokeswoman Svetlana Petrenko said.
Has the plane's model been involved in accidents before?
The SSJ100, also known as the Superjet, is a two-engine regional jet put into service in 2011 with considerable fanfare as a signal that Russia's troubled aerospace industry was on the rise.
The plane is largely used in Russia as a replacement for outdated Soviet-era aircraft, but also is used by airlines in other countries, including Armenia and Mexico.
This is the second fatal accident involving the plane.
In 2012, a demonstration flight in Indonesia struck a mountain, killing all 45 aboard.