ANCHORAGE, Alaska - Four Japanese climbers are presumed dead after they were swept up by a powerful avalanche on Alaska's Mount McKinley, North America's tallest peak, the National Park Service said on Saturday.

Authorities said one man in the group survived and hiked down to get help. The avalanche struck early on Thursday, but searchers working that day and on Friday found no bodies or climbing gear, the Park Service said.

Undated handout photo courtesy of the National Park Service shows the Kahiltna Basecamp at Mount McKinley in Alaska. [Photo/Agencies]

"We say 'presumed dead' because we haven't found their bodies," said Maureen McLaughlin, spokeswoman for Denali National Park, where the mountain is located. "We are still up there looking today."

If all four are dead, it would be the worst climbing accident on McKinley since 1992, when four Canadian climbers were killed in a fall, McLaughlin said.

The missing climbers were identified as Yoshiaki Kato, 64; Masako Suda, 50; Michiko Suzuki, 56; and Tamao Suzuki, 63. All are from Miyagi Prefecture in Japan, the Park Service said. They were part of a five-member Miyagi Workers Alpine Federation expedition, and were descending at the time of the accident.

The sole survivor in the group was Hitoshi Ogi, 69, also from Miyagi Prefecture, the Park Service said.

The avalanche struck on McKinley's West Buttress route, the most commonly used path to climb up and down the mountain. The site was about 11,800 feet (3,600 meters) up the 20,320-foot (6,200-meter) mountain, at a point called "Motorcycle Hill."

The area is fairly steep, with a slope of about 35 degrees, and prone to avalanches. But there had not been any avalanche fatalities there until now, McLaughlin said.

Ogi was likely saved by falling into a crevasse, where the avalanche debris swept over him but did not bury him, McLaughlin said. Ogi, who suffered minor injuries, looked unsuccessfully for his climbing partners, then descended to the mountain's 7,200-foot (2,200-meter) elevation base camp to ask for help, she said.

All five were roped together, but the rope broke in the avalanche, McLaughlin said.

National Park Service handout photo dated Jan 11, 2011 shows Mount McKinley in Alaska. [Photo/Agencies]

"His partners may have fallen into the same crevasse he was in, or they may have continued further down and fallen into another crevasse," she said.

The avalanche was about 200 feet (61 meters) wide, and it slid about 800 feet (245 meters) down the mountain, she said.

Park rangers and volunteers, now equipped with a search dog, will continue to probe the avalanche site on Saturday, McLaughlin said.

McKinley's climbing season runs from late April to early July. In a typical year, 1,200 to 1,300 climbers attempt to scale the peak.

Last month, in separate falling accidents, a German climber and a Finnish skier were killed on McKinley.

On the second day of rescue efforts, climbers skirt the edge of the debris field from a June 14, 2012 avalanche. [ Photo/Agencies]