Three renowned mountain climbers were presumed dead after they went missing following an avalanche at Canada's Banff National Park, park officials and the outdoor apparel company, the North Face, sponsoring them said Thursday.

The North Face confirmed that American Jess Roskelley and Austrians David Lama and Hansjorg Auer disappeared while attempting to climb the east face of Howse Peak on the Icefields Parkway. The three men are members of the company's Global Athlete Team, the North Face said in a statement.

"They are missing, and local search and rescue has assumed the worst," the spokesman said in the statement. "We are doing everything we can to support their families, friends and the climbing community during this difficult time. We ask that you keep our athletes and their loved ones in your hearts and thoughts."

Parks Canada’s mountain safety team responded by helicopter early Wednesday after the climbers were reported missing. Park officials "observed signs of multiple avalanches and debris containing climbing equipment," Stephen Holeczi, a visitor safety specialist, said Thursday in a statement. 

"Based on the assessment of the scene, all three members of the party are presumed to be deceased... Parks Canada extends its sincerest condolences to the families, friends and loved ones of the mountaineers," the statement said.

Holeczi said his team suspect it was a Size 3 avalanche, which typically run up to 3,200 feet — big enough to bury a car or destroy a small building or break a few trees.

Ash Routen, an outdoor adventure writer based in England, said the death of the three climbers would be a heavy loss for the sport.

“It’s always a shock when any climber dies, particularly those that are very well publicized, but perhaps people might be a little more shocked that it wasn’t an 8,000-metre peak with a high death rate in the Himalayas,” Routen, who has been closely following the careers of Lama and Auer, said. “Inherently all mountains carry risk... You can just be in the wrong place at the wrong time.”

According to the North Face's website, Lama was the son of a Nepali mountain guide and a nurse from Austria. He was "just five years old when legendary Everest mountaineer Peter Habeler discovered his 'extraordinary feeling for rocks.' By the time he was fifteen, the youngster had taken the climbing world by storm and certainly proved Peter correct."

Roskelley was 20 years old when he summited Mount Everest with his father John Roskelley, who himself was one of the best American mountaineers of his era.

John Roskelley told the Spokesman-Review Thursday that the route his son and the other climbers were attempting was first done in 2000.

"It's just one of those routes where you have to have the right conditions or it turns into a nightmare. This is one of those trips where it turned into a nightmare," John Roskelly said.

In 2007, Auer climbed a 2,700-foot route in the Italian Dolomites without ropes and his attempt was considered the hardest free solo in the world until Alex Honnold’s rope-less ascent of El Capitan in Yosemite National Park in 2017.