As a Mount Everest cleaning crew collected food wrappers, oxygen tanks and other garbage discarded by this year’s record horde of mountaineers, they discovered something far more disturbing in the melting snow ― human remains.

Four corpses were found amid more than 24,000 pounds of garbage removed from the mountain during a 45-day cleaning, The Associated Press reported. Tourism Department official Danduraj Ghimire said the remains were taken to a Kathmandu hospital to be identified.

Hundreds of people have died on Everest since the 1920s and many of the bodies remain frozen on the mountain, unreachable without extraordinary risk and expense. It wasn’t clear when the latest deaths occurred, according to Reuters.

The grim finds were reported less than three weeks after American climber Christopher John Kulish, 61, died while climbing Everest, pushing this year’s death toll on the Nepali side to at least nine.

Days before Kulish’s death, British climber Robin Haynes Fisher, 44, died in the so-called death zone, a point near the mountain’s summit named for its dangerously low oxygen levels.

Adding to the perils of climbing earth’s highest peak, overcrowding on Everest has become a serious issue as mountaineers rush to summit during a relatively short climbing season from March to May.

Last month, a photo taken by climber Nirmal Purja went viral online and throughout international media outlets, showing a long queue of mountaineers winding up to the summit.