Recovery efforts on Alaska's Mount McKinley have been halted on Sunday due to the environmental dangers following an avalanche that is believed to have killed four Japanese climbers.

The National Park Service announced on Sunday that the avalanche may have not immediately killed the climbers. However, it appears they were pushed into a crevasse on the mountain over 100 feet deep, the Associated Press reported.

A ranger lowered himself into the crevasse that the party's sole survivor fell into after the avalanche. The ranger began investigating the scene, searching through the snow and debris far beneath the surface of the glacier. The search had to be permanently suspended after a ranger discovered a climbing rope at the bottom of the crevasse where the Japanese climbers are believed to have died. He began to dig further but encountered compacted ice and snow, MSNBC reported.

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, reported CNN. While probing through the debris roughly 30 meters below the glacier surface, Chenoweth found a broken rope matching the Japanese team's rope.

However, at this time, continuing the search is deemed to be too dangerous.

Due to the danger of ice fall within the crevasse, it was decided to permanently suspend the recovery efforts, the park service said in a news release, according to MSNBC.

The National Park service confirmed that they believe that the crevasse is where the four climbers perished.  

We believe this is their final resting place, said Kris Fister, as spokeswoman for the National Park Service.

The four climbers were identified as Yoshiaki Kato, 64; Masako Suda, 50; Michiko Suzuki 56; and Tamao Suzuki, 63. The only survivor of the party, Hitoshi Ogi, 69, was able to report the avalanche at a base camp on Thursday.

The climbers were part of a team of Miyagi Workers Alpine Federation expedition. They were all from Miyagi Prefecture in Japan, said the park service.

The three men and two women were roped together as they were descending down the crevasse. Ogi was the last person on the rope and closest to the surface when the team fell. He struggled free and alerted the authorities.

Mount McKinley is also known as Denali. It is the tallest peak in North America with an elevation of 20,320 feet. The climbing season at McKinley runs from late April until early July. More than 1,200 people attempt to reach the peak each year.

This season, there have been six deaths on McKinley, named after the former president.