An avalanche swept down the east side of 10,810-foot Howse Peak on the Icefields Parkway at the border of Alberta and British Columbia on Wednesday, where three of the world’s best alpine climbers were known to have been climbing. Now David Lama, Hansjoerg Auer, and Jess Roskelley are missing and presumed dead, according to a spokesperson for Parks Canada.

“Parks Canada visitor safety specialists immediately responded by air and observed signs of multiple avalanches and debris containing climbing equipment,” according to Amy Krause, for Parks Canada, the organization conducting the search in Banff National Park. “Based on the assessment of the scene, all three members of the party are presumed to be deceased. Further investigation is underway but recovery efforts are not currently possible due to additional avalanches and dangerous conditions at the scene.” Parks Canada did not release the names of the climbers.

The climbers were believed to have been attempting a notorious route called M16, first established by Steve House, Barry Blanchard, and Scott Backes in 1999. Recounting that ascent in a Facebook post years later, House wrote that he climbed “one of the hardest pitches of my life.” He also alluded to a “king line” that off-shoots M16, which would be even harder. House wrote: “Years later and M16 awaits a second ascent and the king line awaits. #unclimbed #whoisitgonnabe?”

View Images In October 2018, Lama made the first ascent of Nepal's Lunag Ri—solo—on his fourth attempt. He also made the first free ascent of the Southeast Ridge of Cerro Torre, a feat which made him a National Geographic Adventurer of the Year in 2013. Photograph by David Lama, Red Bull Content Pool

David Lama, 28, of Austria, is a National Geographic Adventurer of the Year who recently soloed the first ascent of Lunag Ri in Nepal. This mountain required four attempts over four years to complete, and it was the site of an incident in which his partner, the seasoned American mountaineer Conrad Anker, sustained an altitude-induced heart attack. Lama helped Anker get off the mountain, saving his life.

View Images Hansjoerg Auer's 2007 free solo climb of a 3,000-foot route on the South face of Marmolada in the Dolomites is considered on par with Alex Honnold's ropeless climb of 3,000-foot El Capitan in Yosemite National Park. Photograph by Damiano Levati, Red Bull Content Pool

Hansjoerg Auer, 35, also of Austria, is one of the boldest and best climbers in the world. In 2007, Auer free-soloed “The Fish” (5.12c), a 3,000-foot route on the south face of Marmolada in the Dolomites. The degree of difficulty and commitment of that solo was considered on par with Alex Honnold’s much more widely known free solo of El Capitan in 2017. In recent years, Auer had turned his attention to soloing and climbing first ascents on difficult 7,000-meter mountains in the Himalaya and the Karakoram, such as Lupghar Sar West (7,157 meters) in Pakistan.

Jess Roskelley, 36, is an American mountaineer and the son of pioneering mountain climber John Roskelley. In 2003 at age 20, Jess, climbing with his father, became the youngest American to summit Mount Everest (a distinction later usurped by Jordan Romero). Some of his most notable accomplishments took place in Alaska, including the first ascent of Mount Huntington's complete South Ridge. He’s also climbed Fitz Roy and Cerro Torre in Patagonia, Argentina, and has amassed over a dozen hard, technical first ascents in the Canadian Rockies and Alaska.

On Facebook, John Roskelley wrote, “As I write this, I know from speaking with the Park Service and rescue personnel yesterday that Jess, David and Hansjorg are presumed dead. It is with a heavy heart I have to say this, but they were hit by a massive avalanche off Mt. Howse sometime on Tuesday and there was visible evidence they perished. Thank you all for your prayers and thoughts.”