Yuri Yudin - Telegraph Investigators found footprints in the snow of eight or nine people who were wearing socks, a single shoe or were barefoot. The footsteps led towards a dense forest but disappeared after 500 metres. The first two bodies, of two men, barefoot and dressed only in their underclothes, were found at the edge of the forest near the remains of a fire. The next three bodies - of Dyatlov and another man and a woman - were found between the fire and the tent, suggesting that they had been trying to return to the tent. Autopsies failed to find any evidence of foul play . An inquest concluded that all five had died of hypothermia. Two months later, however, the partially-dressed bodies of the other four members of the team were discovered in a forest ravine, not far from the first two bodies. They appeared to have suffered traumatic pressure or crush injuries, and the tongue of one had been ripped out. Otherwise there were no external injuries, but tests conducted on their bodies and clothing showed small traces of radiation. The case was investigated by the Soviet military which, after concluding that the group had died from some unspecified "natural force they were unable to overcome," closed the file and classified it secret. Skiers and other travellers were barred from the area for three years. Interest was rekindled in the 1990s when an investigator who had worked on the original case wrote an article entitled "Secret of the Fireballs," in which he suggested that the victims had been killed by some kind of energy from strange fireballs seen in the sky at the time by other students hiking nearby, by local tribesmen and by members of the military search teams. His account sparked a host of theories - none of which fitted with the evidence. The simplest suggestion was that an avalanche had forced the hikers to flee their camp. But while this would explain the ripped tent, which the skiers might have had to cut open from the inside to leave, there were no signs that any such natural event had occurred. A doctor involved in the original autopsies told investigators that only an explosion of some kind could have caused the sort of internal injuries suffered by several of the victims, and some have suggested that their deaths may have been caused by the explosion of a Soviet test missile of some kind. Yet there is no record of rockets being fired at that time from the nearest cosmodrome, which was in Kazakhstan. The sole survivor, Yuri Yudin, was born on July 19 1937, and after the Dyatlov Pass Incident rose to become an administrator in the Solikamsk Perm region of Russia. He always felt that the Soviet military had probably been responsible in some way. In an interview last year he recalled that he had been asked to identify the owner of everything found at the scene, but had failed to find a match for a piece of cloth that seemed to be of military origin, or for a pair of glasses, a pair of skis and a piece of a ski, leading him to suspect that the military had found the tent before the volunteer rescuers. Yudin recalled that the authorities had seemed more interested in why the hikers were in the area in the first place than in how they died. "If they were really killed by a natural force, then there would be no secret, and we would not be talking about this 53 years on," he observed. In March this year the Hollywood director Renny Harlin released The Dyatlov Pass Incident, a horror film in which a group of 21st-century American students shoot a documentary about the events of February 1959 and find history repeating itself. But there is still no proof of what really happened. "If I had a chance to ask God just one question, it would be, 'What really happened to my friends that night?"" Yudin said. Yuri Yudin, born July 19 1937, died April 27 2013