Four of five members of a Japanese team are presumed dead on Mount McKinley in Denali National Park after an avalanche swept over them as they descended the West Buttress.

The avalanche hit about 2 a.m. Thursday as the team was moving down Motorcycle Hill near 11,800 feet on the mountain, park officials said Saturday.

The five-member Miyagi Workers Alpine Federation expedition was traveling as one rope team, although the rope broke during the avalanche, said Denali spokeswoman Maureen McLaughlin.

"One team member survived the event. Hitoshi Ogi, age 69 of Miyagi Prefecture, was swept into a crevasse and subsequently climbed out with minor injuries," she said in a release. "Ogi was unable to locate his teammates in the avalanche debris. Throughout the day, Ogi descended solo to the Kahiltna Basecamp at 7,200 feet, where he reported the accident shortly after 4 p.m."

Two park rangers flew to the avalanche path in the park’s A-Star B3 helicopter to conduct an aerial hasty search. There was no sign of the missing climbers or their gear in the avalanche debris. In light of the time elapsed, it is presumed that the four perished in the accident, said Ms. McLaughlin.

NPS rangers and volunteers began probing the debris zone on Friday to look for signs of the climbers. The four missing climbers include Mr. Yoshiaki Kato, age 64; Ms. Masako Suda, age 50; Ms. Michiko Suzuki, age 56; and Mr. Tamao Suzuki, age 63. All are from Miyagi Prefecture, Japan.

It was not mentioned whether the group had summited McKinley.

As of June 16, there were 395 mountaineers attempting routes on Mt. McKinley, the majority on the West Buttress route. Out of the 630 climbers that have already returned from expeditions this season, 234, or 37 percent, reported reaching the summit.

Substantial snowfall and windy conditions in recent weeks have kept most climbers from reaching the top.