Roopkund Lake, Skeleton Lake, hikers Roopkund Lake, the scene of what was once believed to be one of the world's deadliest hailstorms, is located at an altitude of 16,500 feet in India. (Photo: Vishwas Krishnamurthy/Shutterstock)

High in an uninhabited region of the Himalayan mountains of India lies a lake with a dark secret.

Known officially as Roopkund Lake, its notoriety has given rise to darker nicknames like Mystery Lake or Skeleton Lake. Covered in thick ice and snow for much of the year, Roopkund gives up its ghosts for only a few warm weeks of the year. It's then, in its clear blue-green waters and around its shores, when the remains of a disaster are revealed.

When a British park ranger happened upon the scene in 1942, he came across hundreds upon hundreds of skulls and bones. The lake sits at 16,500 feet (roughly 5,000 meters) above sea level. Because of the frigid cold of the region, many of the bodies still had hair, clothing and even flesh. The site of what appeared to be a relatively recent massacre was enough for the British government — which was in the thick of World War II — to assume a Japanese land invasion had gone awry.

Human bones at Roopkund Lake, skeleton Lake The slopes leading down to the lake are littered with human bones, some of which have been arranged like this. (Photo: Awanish Tirkey/Shutterstock)

An investigation calmed fears of an invasion after it was determined that the bones were of ancient origin, but the bigger mystery of what had killed hundreds of people remained. In 2004, a team sent by National Geographic discovered that not only were the remains from 850 A.D., but that the victims had all died the same way: severe blows to the head and shoulders.

"The only plausible explanation for so many people sustaining such similar injuries at the same time is something that fell from the sky," said Dr. Subhash Walimbe, a physical anthropologist, told the Telegraph at the time. "The injuries were all to the top of the skull and not to other bones in the body, so they must have come from above. Our view is that death was caused by extremely large hailstones."

But new research published in Nature Communications adds a dramatic twist to the story. Looking at the DNA of 38 of the bodies, scientists now say those who perished didn't die in one horrific moment. There are at least three genetically distinct groups represented in their research — a fraction of the hundreds of bodies discovered there — and they died in events that played out over more than 1,000 years.

A team led by Éadaoin Harney, a PhD candidate in organismic and evolutionary biology at Harvard University, analyzed the remains using radiocarbon dating and osteological analysis, among other approaches, and here's what that work uncovered: "A group of 23 individuals have ancestry that falls within the range of variation of present-day South Asians. A further 14 have ancestry typical of the eastern Mediterranean. We also identify one individual with Southeast Asian-related ancestry."

"These findings refute previous suggestions that the skeletons of Roopkund Lake were deposited in a single catastrophic event."

But what about the hailstorm theory?

The hailstorm theory had weight for such a long time because it made sense based on what scientists first found. With no shelter to speak of and to avoid the stinging ice, dozens may have began climbing back up the steep incline surrounding Roopkund. Anthropologists studying the impressions left on skulls and bones say the hail quickly became deadly, with the killer blows coming from bowling-ball hail as large as 9 inches in diameter.

It's reasonable to assume that with so much ice falling, many would have retreated from the shore and dove under the water. Unfortunately, Roopkund's relatively shallow pool would have offered little protection from massive hailstones traveling at more than 100 mph.

"We retrieved a number of skulls which showed short, deep cracks," added Walimbe. "These were caused not by a landslide or an avalanche but by blunt, round objects about the size of cricket balls."

Legend has it

A view of hikers making their way around Roopkund, the skeleton lake Hikers make their way around Roopkund. (Photo: Akash Dhyan/Shutterstock)

Visit Roopkund today via one of the many guided treks available and, if your timing is right, you'll come across the remains. While tourists interested in macabre souvenirs have removed many of the bones and other artifacts from the site, it's said that you can still see dozens of skeletons at the bottom of the clear glacial lake. Anthropologists believe there may be as many 600 bodies buried in the surrounding ice and earth.

Based on a legend handed down by locals over the centuries, it's possible there may have been survivors who passed along the horror of what took place at Roopkund. The story goes that a medieval monarch named King Jasdhawal, on pilgrimage with his queen and royal entourage, disobeyed the Hindu goddess Mata.

"So furious was the Mata, that she enlisted Latu a local deity," Dinesh Kuniyal, a local Hindu priest told IndiaHikes. "With Latu's help she created thunderstorms and avalanches. Huge hailstones rained down on the king's army. The army of Kannauj didn’t have a chance. All of them perished in Mata’s fury. It is their skeletons at the Roopkund lake."

More work to be done

Interestingly, the new team's work doesn't rule out the hailstorm theory completely.

"Our study deepens the Roopkund mystery in many ways," study co-author Niraj Rai, head of the Ancient DNA Lab at Birbal Sahni Institute of Palaeosciences in India, told Vice in an email.

In fact, the team will continue to study more of the human remains in an effort to find more clues to this ongoing mystery.

Editor update: This story has been updated with new information since it was published in October 2015.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

The legend of Skeleton Lake just got weirder
In 850 A.D., those gathered around a glacial lake perished from one of nature's most deadly phenomena. Or so we thought. New evidence deepens the mystery.