Investigators have found one of the two flight recorders at a crash site of a Russian MiG-31 Foxhound fighter jet in the Urals, a source in the investigation committee said.
The jet exploded in a fireball minutes after taking off from a military airfield in the Perm region in the early hours of Tuesday. Both pilots were killed in the crash.
"We have found one of the flight recorders and will continue the investigation of the crash site tomorrow," the source told RIA Novosti.
A technical failure is being considered as a possible cause of the crash.
Relatively few MiG-31s have been modernized to the MiG-31BM version since the heavy interceptor entered service with the Russian Air Force in 1982. Experts believe that technical problems are inevitable on aircraft whose service life is nearing its end without a thorough overhaul.
A similar jet crashed in the Urals region less than a year ago, but the pilots managed to parachute to safety.
The Air Force has grounded all MiG-31s in its fleet and said the flight ban would continue until the cause of the crash is established.