Russian security officials investigating the possibility of terrorist involvement in the destruction of two airplanes that crashed within minutes of each other have said they were likely to have been accidents.
President Vladimir Putin ordered the FSB security service to investigate the case, something it is normally only asked to do where terrorism is suspected.
But the FSB officials claim to have no evidence to support the possibility of a terrorist act.
Russia's chief prosecutor has said there is no clear view of what caused two plane crashes that killed 89 people.
He said they were examining a number of possibilities, among them a terrorist act and human and technical factors.
President Putin has called a day of national mourning tomorrow.
There were no survivors from either plane, which had been carrying a total of 90 passengers and crew. However, flight recorders from both planes have been found.
One of the aircraft, the Sibir Airlines Tu-154, which was carrying 46 people to the Black Sea resort of Sochi, crashed around 80 miles from Rostov-on-Don, near the Ukrainian border.
It is reported to have sent out a hijack or distress signal before it vanished from the radar.
At almost the same time, another plane, the Volga-Aviaexpress Tu-134, which was taking 44 people to Volgograd went down about 100 miles south of Moscow.
There are reports that witnesses on the ground saw an explosion in the air just before the crash.
