The Dyatlov Pass incident was an event that resulted in the death of nine skiers north of the Ural mountains on the night of February 2, 1959. The incident happened on the east coast of Kholat Syakhl, whose name in Mansi means “Mountain of the Dead.” Since then, the mountain pass where the incident occurred is called Dyatlov Pass, based on the name of the group’s leader, Igor Dyatlov.

The absence of witnesses and the subsequent investigations concerning the death of skiers inspired intense speculation. Investigators determined that the skiers tore their tent inside out, fleeing on foot under heavy snowfall. Although the bodies show no signs of struggle, two victims had fractured skulls and two broken ribs. Soviet authorities determined that an “unknown compelling force” had caused the deaths; access to the region was consequently blocked for hikers and adventurers for three years after the incident. Due to the lack of survivors, the chronology of events remains uncertain.

http://en.wikipedia.org/wiki/Dyatlov_Pass_incident