http://www.slate.com/blogs/atlas_obscura/2013/05/24/an_indian_lake_surrounded_by_hundreds_of_ancient_skeletons_the_surprise.html

From Slate:

Skeleton Lake of Roopkund, India. The Surprise Is What Killed Them …

By Atlas Obscura | Posted Friday, May 24, 2013, at 7:30 AM

"In 1942 a British forest guard in Roopkund, India, made an alarming discovery. More than three miles above sea level, he stumbled across a frozen lake surrounded by hundreds of human skeletons. That summer, the melting ice revealed even more remains, floating in the water and lying haphazardly around the lake's edges. 

Since this was the height of World War II, there were fears that the skeletons might belong to Japanese soldiers who had died of exposure while sneaking through India. The British government, terrified of a Japanese land invasion, sent a team of investigators to determine whether this was true. Upon examination they realized these bones weren't Japanese soldiers at all, but of a much much older vintage. But what killed them? Many theories were put forth, including an epidemic, landslide, and ritual suicide. For six decades, no one was able to shed light on the mystery of "Skeleton Lake."

In 2004 a scientific expedition offered the first plausible explanation of the mysterious deaths. The answer was stranger than anyone had guessed...."