Dyatlov Pass incident

The Dyatlov Pass incident was an event in which nine Soviet ski hikers died in the northern Ural Mountains between February 1 and 2, 1959, under uncertain circumstances. The experienced trekking group from the Ural Polytechnical Institute, led by Igor Dyatlov, had established a camp on the eastern slopes of Kholat Syakhl in the Russian SFSR of the Soviet Union. Overnight, something caused them to cut their way out of their tent and flee the campsite while inadequately dressed for the heavy snowfall and subzero temperatures.

After the group's bodies were discovered, an investigation by Soviet authorities determined that six of them had died from hypothermia while the other three had been killed by physical trauma. One victim had major skull damage, two had severe chest trauma, and another had a small crack in his skull.

Source: Wikipedia