David Lama, Jess Roskelley, and Hansjörg Auer were "caught in an avalanche earlier this week while attempting to climb the east face of Howse Peak in Alberta," a North Face spokesman said, CNN reported.
The three men, one American and two Europeans, are members of the company's Global Athlete Team.
"They are missing, and local search and rescue has assumed the worst," the spokesman said.
Hansjörg Auer is a skilled free solo climber from Austria.
"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."
After the climbers were reported missing Wednesday, park officials searched for them via air and "observed signs of multiple avalanches and debris containing climbing equipment," Parks Canada said in a statement.
"Based on the assessment of the scene, all three members of the party are presumed to be deceased," the statement noted.
Eli Francovich, an outdoors reporter with the Spokesman Review newspaper in Spokane, Washington, spoke with Roskelley's father, John Roskelley, who confirmed that his son was missing.
"Jess was going to check in Tuesday and didn't, and John called Parks Canada. They sent out a helicopter. They saw an avalanche debris field and one partially buried body," Francovich told CNN partner CBC News.
Park officials said they are investigating the incident but recovery efforts were not currently possible because of the "rising avalanche in the area."
It appears the climbers were caught in a size three avalanche, said Chelsey Dawes, a spokeswoman with Parks Canada.
The east face of Howse Peak is a remote and an exceptionally difficult climb, with mixed rock and ice routes requiring advanced alpine mountaineering skills, officials said.