Russian investigators are warning that heavy damage to both flight-recorders of the crashed Aeroflot-Nord Boeing 737-500 means extracting useful data will take additional time.
The Interstate Aviation Committee (MAK) has started examining the cockpit-voice and flight-data recorders from the aircraft which came down in southern Perm yesterday while arriving from Moscow.
MAK states: "During inspection of the flight recorders in our technical centre, serious damage was discovered to both tape mechanisms for the voice and data parameters.
"To decode the recordings, given their poor condition, requires additional work using special equipment."
It says the investigative commission will include US and French participants, representing the manufacturing states of the airframe and engines. A representative from the UK will also take part because the aircraft was Bermuda-registered.