The Dyatlov Pass incident refers to an event that resulted in the deaths of nine ski hikers in the northern Ural mountains on the night of February 2, 1959. It happened on the east shoulder of the mountain Kholat Syakhl (Холат Сяхл) (a Mansi name, meaning Mountain of the Dead). The mountain pass where the incident occurred has since been named Dyatlov Pass (Перевал Дятлова) after the group's leader, Igor Dyatlov (Игорь Дятлов). The lack of eyewitnesses has inspired much speculation. Soviet investigators determined only that "a compelling unknown force" had caused the deaths. Access to the area was barred for skiers and other adventurers for three years after the incident. The chronology of the incident remains unclear due to the lack of survivors.Investigators at the time determined that the hikers tore open their tent from within, departing barefoot into heavy snow and a temperature of −30°C. Though the corpses showed no signs of struggle, two victims had fractured skulls, two had broken ribs, and one was missing her tongue. Their clothing, when tested, was found to be highly radioactive.