The news came as some aviation experts questioned initial reports from investigators that the crash, which killed all 88 people on board the flight, had been caused by equipment failure.
The work on the black boxes will likely take three or four weeks, Valery Vlasov, head of the Volga and Urals branch of the Emergency Situations Ministry, said Monday on Radio Rossii.
The flight, which originated in Moscow, crashed minutes before the scheduled landing in Perm. Witnesses said the plane burst into a ball of fire at an altitude of about one kilometer, and investigators said debris from the aircraft was scattered across an area of 10 square kilometers.
Alexander Bastrykin, chief of the Investigative Committee of the Prosecutor General Office, said Sunday that a fire in one of the aircraft's two engines was likely responsible for the catastrophe.
But there were conflicting comments from aviation experts on Monday, with some saying human error or even a bird could have caused the catastrophe.
"The reason for the engine catching fire, in theory, could have been a large bird flying into the turbine," said Anatoly Kvochur, a veteran test pilot, Interfax reported.
Kvochur said spontaneous fires in aircraft engines were rare and were usually put out easily by automatic extinguisher systems on board.
Human error could also have been a factor, Interfax reported, citing an unidentified source in the Central Aerodynamics Institute.
"An experienced pilot is quite able to land a jet with one working engine," the source said.
The tabloid Tvoi Den reported Monday that a flight controller responsible for helping the plane land said one of the pilots had ignored instructions during the approach.
After further examination of the wreckage for traces of explosives, investigators from the Perm branch of the Federal Security Service said Monday they had ruled out terrorism as a possible cause of the crash, Itar-Tass reported.
A technical commission from the Federal Air Transportation Agency had begun investigating Aeroflot Nord, a subsidiary of national airline Aeroflot, for possible violations of piloting or technical maintenance regulations, and was also examining the company's general activities.
Aeroflot Nord spokesman Anton Popov declined immediate comment Monday.
Prime Minister Vladimir Putin was shown on national television Monday ordering Transportation Minister Igor Levitin to take personal control of the investigation in nationally televised comments.
Relatives of the crash victims have been asked to submit blood samples so that comparative DNA tests can be conducted to identify the bodies, Channel One reported Monday.
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