On February 2, 1959, nine ski hikers died in the northern Ural Mountains in Russia in a bizarre incident. Apparently, the hikers tore open their tent from within and wandered into the night barefooted, whereupon most died of hypothermia. While the corpses showed no sign of struggle, two had fractured skulls, two had broken ribs, and one was missing her tongue. According to some reports, their clothing contained high levels of radioactivity. Soviet investigators ruled "a compelling unknown force" as the cause of the incident.