A group of eight tourists have gone missing in Russia's infamous Dyatlov Pass where nine people died in unexplained circumstances in 1959.
The tourists from Moscow ventured into the pass in the rural region of Ural and had not returned by Wednesday morning as expected, Newsweek reported, citing E1.RU.
A source told the Russian outlet: 'They were supposed to leave at eight o'clock this morning. But they have not returned yet and there is no contact with them.'
The case of the nine missing people in February 1959 sparked conspiracy theories around Soviet military experiments, Yeti attacks, and even alien contact.
The eight tourists had made the journey to pay tribute to the group, who had died there over 60 years ago, E1.RU reported the source as saying.
The Ministry of Emergency Situations in the Sverdlovsk Region told the outlet that it was aware of three registered groups visiting the pass. All three groups were in contact with the department, it said, adding 'If the group is not registered, then there have been no reports of missing people either.'
Last year, Russian prosecutors ruled the Dyatlov skiers died of hypothermia in 1959 after stripping off their clothes and fleeing in terror for unknown reasons.
But an article published in the scientific journal Communications Earth and Environment in January this year contradicted the ruling.
In the article, scientists presented evidence that suggested a small, delayed avalanche was likely responsible for the group's gruesome injuries. Led by 23-year-old Ifor Dyatlov, the experienced skiers failed to finish their 220mile-ski trek, sparking a huge manhunt.
Investigators later discovered their frozen bodies - many with missing body parts, others naked, and some with inexplicable injuries, leading to decade-long conspiracy theories that persist to this day.
What is known of that fateful night is that Ural Polytechnic students - seven men and two women, had made camp for the night at the foot of Kholat Syakhl, the Dead Mountain.Investigators say the nine fled in terror - and ran through the snow a mile or so down the mountain - from their tents in the deep nighttime cold, not having time to dress.
Their tent had been mysteriously slashed from the inside, their camp was deserted and they had left their clothes and belongings behind.
The empty tent baffled investigators, because it still contained items of clothing and pairs of shoes - implying that some of the students had ventured out into the wilderness barefoot and without coats.
Days after investigators found the tent the first two bodies were discovered.
Yuri Doroshenko and Yuri Krivonischenko were found lying in the snow on flat land near a river, a mile from the tent, next to the remains of a long burnt-out fire.Around 350 yards away lay the corpse of Dyatlov, the engineering student who had put the expedition together and was its leader.
His name would later be given to the area where the tragedy took place, as well as the incident itself.
Nearby, a search dog sniffed out the remains of Zina Kolmogorova, 22, under four inches of snow, and then that of Rustem Slobodin.
The bodies were in a line 200 yards apart, as if they had been trying to crawl behind each other back up to the shelter of the tent, but never made it.
The final bodies were not found until the snow melted two months later in a ravine, with fractured skulls and chest injuries.
The tongue and eyes of Lyudmila Dubinina, 21, and Semen Zolotarev, 38, were missing.
They were discovered under 15 feet of snow in a den they had desperately hollowed out for themselves before succumbing to the cold.
In 2019, Russian authorities made the surprise announcement that they planned to reopen the case in a bid to solve the mystery once and for all.
Last year, senior state prosecutor Andrei Kuryakov revealed the group's tent had been in danger from an avalanche and that the party rushed from their camp to shield behind a ridge.
'This was a natural avalanche limiter. They did everything right'
But he claimed that when the group turned around, they had lost sight of their tent.
'Visibility was 16 metres. They lit a fire and then searched for their tent - but it had vanished in the whiteout after the avalanche.
He revealed the group 'froze to death in temperatures of between minus 40C and minus 45C'. 'It was an heroic fight. There was no panic, but they had no chance in these circumstances.'
An experiment was conducted in an attempt to recreate the circumstances faced by the Soviet skiers.
But in January, scientists put forward the theory that they were killed by an avalanche that resulted in the group's bodies being scattered over the mountain.
The theory was first proposed in 1959, but people argue it still doesn't stack up.
Doubters say the slope where the team had set up the tent was too flat to allow for an avalanche, and that there was no snowfall on the night of February 1 to increase the weight enough to trigger a collapse.
Furthermore, people killed in avalanches typically asphyxiate, which is not in-line with the blunt force trauma injuries suffered by the people in the group.
But scientists argue the slope was not actually that flat, and - utilising animation techniques used in the Disney movie 'Frozen' - simulated the impact an avalanche can have on the human body, which they used to back up their claim.
They also noted that the Dyatalov group’s diary mentioned strong winds on the night, which could have brought snow from further up the mountains to increase the volume of snow already bearing down on the campers.
The scientists believe the avalanche may have been caused by a cut in the snow made by the group as they set up camp.
They had flattened a small section of the surface to form a 'shoulder' or ridge in the slope - believing it would shield them from the worst of the fierce winds.A combination of other factors - including the unusual terrain and strong, icy winds - later triggered the 'slab avalanche' that apparently chased the team out of their tent and left them to freeze to death - semi-naked - in -13F (-25C) temperatures.
A slab avalanche occurs when a weak layer lies lower down in a snowpack. When it breaks off, the compressed snow on top is also pulled along the slope.
Professor Alexander Puzrin, of the Swiss Federal Institute of Technology (EPFL), Zurich, and corresponding author of the study, said the cut, combined with unusual terrain and a rare weather event called katabatic winds was enough to trigger the avalanche.
Katabatic winds carry air down a slope under the force of gravity, transporting snow in the process.
Professor Puzrin said: 'The katabatic wind probably drifted the snow and allowed an extra load to build up slowly. At a certain point, a crack could have formed and propagated, causing the snow slab to release.'
Co-author Dr Johan Gaume, head of EPFL's Snow and Avalanche Simulation Laboratory, said: 'We use data on snow friction and local topography to prove a small slab avalanche could occur on a gentle slope, leaving few traces behind.'
