Russian investigators are trying to determine why a passenger airliner crashed while trying to land in the city of Kazan, killing all 50 people aboard.
Video shown Monday by Russian television stations shows the plane plunging to the ground in a near-vertical descent and then exploding.
Officials say the Tatarstan Airlines flight from Moscow was making a second attempt to land late Sunday when it went down in Kazan, 720 kilometers east of the Russian capital.
Investigators say they have found both black boxes, which record the plane's flight data and the crew's conversations. They say they are looking into all possibilities, including pilot error and technical failure.
Associated Press reports government experts from the United States (NTSB and FAA), as well as the airline's manufacturer, were heading to the scene to help Russian investigators.
Officials say that because the Boeing 737 exploded on impact, it could take weeks to identify the victims' remains.
Friends and relatives of the victims gathered Monday in Kazan, Tatarstan's capital, to mourn the deaths.