The Dyatlov Pass Accident refers to an incident that resulted in the death of nine ski hikers in the northern Ural mountains. The incident happened on the night of February 2, 1959 on the east shoulder of the mountain Kholat Syakhl(a Mansi name, meaning Mountain of the Dead). The mountain pass where the accident occurred has been named Dyatlov Pass after the group's leader, Igor Dyatlov. The mysterious circumstances of the hikers' deaths have inspired much speculation. Investigations of the deaths suggest that the hikers tore open their tent from within, departing barefoot in heavy snow; while the corpses show no signs of struggle, one victim had a fractured skull, two had broken ribs, and one was missing her tongue. The victims' clothing contained high levels of radiation. Soviet investigators determined only that "a compelling unknown force" had caused the deaths, barring entry to the area for years thereafter. The causes of the accident remain unclear. It had been agreed beforehand that Dyatlov would send a telegraph to their sports club as soon as the group returned to Vizhai. It was expected that this would happen no later than February 12, but when this date had passed and no messages had been received, there was no reaction, delays of a few days were common in such expeditions. Only after the relatives of the travelers demanded a rescue operation did the head of the institute send the first rescue groups, consisting of volunteer students and teachers, on February 20. Later, the army and police forces became involved, with planes and helicopters being ordered to join the rescue operation. On February 26, the searchers found the abandoned camp on Kholat Syakhl. The tent was badly damaged. A chain of footsteps could be followed, leading down towards the edge of nearby woods (on the opposite side of the pass, 1.5km north-east), but after 500 meters they were covered with snow. At the forest edge, under a large old pine, the searchers found the remains of a fire, along with the first two dead bodies, those of Krivonischenko and Doroshenko, shoeless and dressed only in their underwear. Between the pine and the camp the searchers found three more corpses - Dyatlov, Kolmogorova and Slobodin - who seemed to have died in poses suggesting that they were attempting to return to the camp. They were found separately at distances of 300, 480 and 630 meters from the pine tree. Searching for the remaining four travelers took more than two months. They were finally found on May 4, under four meters of snow, in a stream valley further into the wood from the pine tree.