Investigators have started analysing the flight recorders retrieved from the Polish presidential Tupolev Tu-154M which crashed at Smolensk yesterday.
Russia's Interstate Aviation Committee (MAK) says that, upon opening the flight-data recorder, investigators found that the tapes were still attached to their reels, but the reels had separated from the drive mechanism - probably as a result of the impact.
MAK says the analysis is being carried out in the presence of Polish delegates. The Polish prime minister's office, and general prosecutor's office, stated yesterday that they intended to participate jointly with Russian investigators in the inquiry.
Circumstances of the accident remain unclear, beyond preliminary indications that the aircraft had been attempting to land at the city's military airport in fog.
The deputy head of Russia's air staff, Alexander Alyoshin, told reporters yesterday that the aircraft had continued to descend towards the airport despite being given the option to divert.
But he pointed out that the crew of the aircraft had the authority to decide whether to continue or abort an approach.
Russia's Aviakor plant, in Samara, undertook work late last year to modernise the two Polish Tu-154Ms under a contract with the country's defence ministry.
This work, it says, included repairs, upgrade of the VIP-configured interior, and servicing of the Soloviev D30-KU engines.