(CNN) -- Recovery efforts on Alaska's Mount McKinley were suspended Sunday because of environmental hazards following an avalanche thought to have killed four Japanese climbers, the National Park Service said.
The avalanche on the western side of the mountain, America's highest peak, was first thought to have occurred on Thursday, the parks service said Sunday. However, rangers later confirmed with climber Hitoshi Ogi, who survived the avalanche, and with teams on the mountain that the slide occurred early Wednesday.
The section where the avalanche took place is roughly 11,800 feet above sea level, park spokeswoman Maureen McLaughlin said Saturday.
The five were traveling on McKinley's West Buttress as one rope team, although the rope broke during the incident, officials said. One climber, Ogi, survived the incident after he was swept into a mountain crevasse and was able to climb out, sustaining a minor hand injury, officials said.
Ogi, 69, was unable to locate his fellow climbers and descended solo to the Kahiltna Basecamp, where he reported the event, according to the park service.
An aerial search took place Thursday, and an initial four-member ground search took place Friday, the park service said. On Saturday, a 10-person crew including rangers, volunteer patrol members, a dog handler and a rescue dog investigated the debris zone left by the avalanche.
"During the search, NPS mountaineering ranger Tucker Chenoweth descended into the same crevasse that the survivor Hitoshi Ogi had fallen into during the avalanche," the parks service said. "While probing through the debris roughly 30 meters below the glacier surface, Chenoweth found a broken rope" matching the Japanese team's rope.
He attempted to dig further "but encountered heavily compacted ice and snow debris," officials said. "Due to the danger of ice fall within the crevasse, it was decided to permanently suspend the recovery efforts."
Male climbers Yoshiaki Kato, 64, and Tamao Suzuki, 63, and female climbers Masako Suda, 50, and Michiko Suzuki, 56, of the Miyagi Workers Alpine Federation expedition are all presumed to have died in the avalanche, the park service said.
The climbers, on their registration forms, indicated their experience included climbing peaks in Africa and Asia, but not McKinley, McLaughlin said.
Named after William McKinley, the 25th president of the United States, the mountain's summit reaches an elevation of 20,320 feet above sea level. The mountain is also known as Denali, an indigenous name meaning "the high one."
The debris path was about 800 feet long and 200 feet wide, officials said. It was in an area where avalanches are known to occur, but not of this magnitude.
There have been six climbing fatalities on Mount McKinley this season, the parks service said. The four Japanese fatalities were the first to occur on the West Buttress route.
In May, a climber died after falling more than 1,000 feet down McKinley's north face. The climber apparently tried to recover a backpack that had started to slide downhill before falling, the park service reported.
That fatality was considered McKinley's first serious incident of the 2012 mountaineering season. Less than a week later, a 36-year-old Finnish mountaineer also died from injuries sustained in a fall during descent.
Since 1932, a total of 120 climbers have died on Mount McKinley, according to the park service.
The Japanese consulate in Anchorage has been in contact with the families and assisted in translating conversations with Ogi.
CNN's David Ariosto and Phil Gast contributed to this report.