The lack of eyewitnesses has inspired much speculation. Soviet investigators simply determined that "a compelling natural 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 because of 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 (−22 °F). Although the corpses showed no signs of struggle, two victims had fractured skulls, two had broken ribs, and one was missing parts of her face due to postmortem decay.
The group was formed for a ski trek across the northern Urals in Sverdlovsk Oblast. Led by Igor Dyatlov, consisted of eight men and two women. Most were students or graduates of Ural Polytechnical Institute, now Ural Federal University.
The goal of the expedition was to reach Otorten, a mountain 10 kilometres (6.2 mi) north of the site of the incident. This route, at that season, was estimated as "Category III", the most difficult. All members were experienced in long ski tours and mountain expeditions.
The group arrived by train at Ivdel, a city at the center of the northern province of Sverdlovsk Oblast on January 25. They then took a truck to Vizhai – the last inhabited settlement so far north. They started their march toward Otorten from Vizhai on January 27. The next day, one of the members (Yuri Yudin) was forced to go back because of illness. The group now consisted of nine people.
Diaries and cameras found around their last camp made it possible to track the group's route up to the day preceding the incident. On January 31, the group arrived at the edge of a highland area and began to prepare for climbing. In a wooded valley they cached surplus food and equipment that would be used for the trip back. The following day (February 1), the hikers started to move through the pass. It seems they planned to get over the pass and make camp for the next night on the opposite side, but because of worsening weather conditions, snowstorms and decreasing visibility, they lost their direction and deviated west, upward towards the top of Kholat Syakhyl. When they realized their mistake, the group decided to stop and set up camp there on the slope of the mountain rather than moving 1.5 kilometres (0.93 mi) downhill to a forested area which would have offered some shelter from the elements. Yuri Yudin, the lone survivor, postulates that "Dyatlov probably did not want to lose the altitude they had gained, or he decided to practice camping on the mountain slope. "
It had been agreed beforehand that Dyatlov would send a telegram 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 Dyatlov had told Yudin that he expected to be longer, and so when this date 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 militsiya forces became involved, with planes and helicopters being ordered to join the rescue operation.
On February 26, the searchers found the abandoned and badly damaged tent on Kholat Syakhl. Mikhail Sharavin, the student who found the tent, said "the tent was half torn down and covered with snow. It was empty, and all the group's belongings and shoes had been left behind." Investigators said the tent had been cut open from inside. A chain of eight or nine sets of footprints, left by several people who were wearing only socks, a single shoe or were barefoot, could be followed and led down toward the edge of nearby woods (on the opposite side of the pass, 1.5 kilometres (0.93 mi) north-east), but after 500 metres (1,600 ft) they were covered with snow. At the forest edge, under a large cedar, the searchers found the remains of a fire, along with the first two bodies, those of Yuri Krivonischenko and Yuri Doroshenko, shoeless and dressed only in their underwear. The branches on the tree were broken up to five meters high, suggesting that a skier had climbed up to look for something, perhaps the camp. Between the cedar and the camp the searchers found three more corpses, Dyatlov, Zina Kolmogorova and Rustem Slobodin, who seemed to have died in poses suggesting that they were attempting to return to the tent. They were found separately at distances of 300, 480 and 630 meters from the 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 ravine 75 meters farther into the woods from the cedar tree. These four were better dressed than the others, and there were signs that those who had died first had apparently relinquished their clothes to the others. Zolotaryov was wearing Dubinina's faux fur coat and hat, while Dubinina's foot was wrapped in a piece of Krivonishenko's wool pants.
A legal inquest started immediately after finding the first five bodies. A medical examination found no injuries which might have led to their deaths, and it was concluded that they had all died of hypothermia. Slobodin had a small crack in his skull, but it was not thought to be a fatal wound.
An examination of the four bodies which were found in May changed the picture. Three of them had fatal injuries: the body of Thibeaux-Brignolles had major skull damage, and both Dubinina and Zolotarev had major chest fractures. According to Dr. Boris Vozrozhdenny, the force required to cause such damage would have been extremely high. He compared it to the force of a car crash. Notably, the bodies had no external wounds related to the bone fractures, as if they were crippled by a high level of pressure. Major external injuries were, however found on Dubinina, who was missing her tongue, eyes, and part of the lips, facial tissue and a fragment of skullbone; however, as she had been lying face-down in a small stream that ran under the snow for weeks and also had extensive skin maceration on the hands, her external injuries are in line with putrefaction in a wet environment and unlikely to be related to her death. There had initially been some speculation that the indigenous Mansi people might have attacked and murdered the group for encroaching upon their lands, but investigation indicated that the nature of their deaths did not support this hypothesis; the hikers' footprints alone were visible, and they showed no sign of hand-to-hand struggle.
Although the temperature was very low, around −25 to −30 °C (−13 to −22 °F) with a storm blowing, the dead were only partially dressed. Some of them had only one shoe, while others had no shoes or wore only socks. Some were found wrapped in snips of ripped clothes that seemed to have been cut from those who were already dead.
Many theories have arisen about the event, from paranormal activity to secret weapons tests, but avalanche damage is considered one of the more plausible explanations for this incident. One scenario under this theory is that moving snow knocked down the tent, ruining the campsite in the night. The party then cut themselves free and mobilized. The snow would likely have contacted them and possibly ruined their boots and extra clothing. Being covered in wet snow in the sub-freezing temperatures created a serious hazard to survival, with exhaustion or unconsciousness from hypothermia possible in under 15 minutes. Thibeaux-Brignolles, Dubinina, Zolotariov, and Kolevatov were moving farther from the site to find help despite their remote location when they fell in the ravine where they were found – three of these bodies had major fractures. Being the only bodies with major injuries and lying 13 feet deep in a ravine could be considered evidence that they fell.
One supporting factor for this theory is that avalanches are not uncommon on any slope that can accumulate snow. Despite claims that the area is not prone to avalanches, slab avalanches do typically occur in new snow and where people are disrupting the snowpack. On the night of the incident, snow was falling, the campsite was situated on a slope, and the campers were disrupting the stability of the snowpack. The tent was also halfway torn down and partially covered with snow – all of which could support the theory of a small avalanche pushing snow into the tent.
Possibly negating the avalanche scenario would be that the investigators saw footprints leading from the campsite, and no obvious avalanche damage was noted. However, the footprints could have been preserved if there was no precipitation in the 25 days before the site was discovered and the supposed avalanche happened after most of the snow fell.
Another theory is that wind going around the Holatchahl mountain created a Kármán vortex street, which resulted in infrasounds that have effects on humans. In my opinion, the aliens are to blame.