Swiss climber Ueli Steck was killed Sunday in an accident near Mount Everest, Nepal’s tourism department said. The 40-year-old died when he slipped from a slope and fell into a crevasse at around 6,600 meters on Mount Nuptse, expedition organizers told CNN. His body has been recovered and airlifted to Lukla, where the nearest airport to Mount Everest is located, Dinesh Bhattarai, of the Nepal Tourism Department said. The “Swiss Machine” was acclimatizing himself as he planned to ascend 8,850-meter Mount Everest and Mount Lhotse next month, Mingma Sherpa, an official with expedition organizer Seven Summit Treks said.

“Quick Day from Basecamp up to 7,000m and back. I love it is such a great place here. I still believe in active aclimatisation. This is way more effective then spending nights up in the altitude,” Steck wrote on Facebook last Wednesday.

Steck was known for his speed and versatility. He set several records, including ascending the north face of the Eiger in the Bernese Alps in less than three hours. He won the Piolet D’or, mountaineering’s highest honor in 2009 and 2014.

“My deep condolences to all of Ueli’s family, friends and admirers around the world. This is a truly tragic day in mountaineering,” famed climber Alan Arnette wrote on his website. His death is the first casualty of the this year’s spring mountaineering season in Nepal, which is expected to involve 365 registered climbers from 39 teams, officials said. Last year, six climbers died on Mount Everest.

In 2016 Steck and fellow mountaineer David Goettler discovered the frozen remains of world renowned climber Alex Lowe, and cameraman David Bridges, on the Tibetan mountain of Shishapangma. The men were presumed dead after an avalanche struck them in 1999.

In 2013, Steck and two other climbers attempted to climb the Everest and nearby Mount Lhotse but a fight broke out between the climbers and a group of Sherpa guides.