GROZNY, July 17 (RIA Novosti) - The most likely reason for the Mi-8 helicopter crash on Saturday in Chechnya was a collision with a mountain, a source close to investigation said.

The source said the helicopter could have collided with the Rogkort mountain. "Other versions are also being checked," the source said.

A Defense Ministry Mi-8 helicopter with nine people on board crashed Saturday at 11.25 in Chechnya. Three crew and five border guards died, a Defense Ministry serviceman was wounded.

Earlier a military prosecutor's office official told RIA Novosti on the phone that a criminal case was opened "for violating flight or flight preparation rules." He said "all possible versions, including fire damage and equipment failure are looked into."