Alaska's Mount Denali is the tallest peak in North America
CNN  — 

The body of an Austrian climber who was last heard from a week ago has been found on the slopes of Alaska’s Mount Denali, authorities said on Friday.

An aerial search spotted the body of Matthias Rimml in the fall zone below Denali Pass, the National Park Service said. His body has not yet been recovered as authorities will rely on a ranger patrol that’s adapted to high altitude to facilitate the effort.

The 35-year-old was alone and was the first registered climber this season to attempt climbing the 20,310-foot peak, the tallest in North America.

“Rimml likely fell on the steep traverse between Denali Pass at 18,200 feet and the 17,200-foot plateau, a notoriously treacherous stretch of the West Buttress route,” the NPS said in the news release.

Rimml, a professional mountain guide from Tirol, Austria, began his climb on April 27 from the 7,200-foot Kahiltna Basecamp.

“Already acclimatized to altitude due to recent climbs,” Rimmi planned the climb alpine-style, according to the NPS, which means traveling fast with light gear. He planned to complete the climb in five days, though he was prepared with food and fuel to last him for 10 days.

The last known phone call he made was on April 30, when he was at about 18,000 feet on the West Buttress of Denali, officials said. He said he was tired, “but he was not in distress,” officials noted in the news release.

“However, since his friend had been receiving periodic check-in calls from Rimml, he grew concerned after several days of silence and notified Denali mountaineering rangers the afternoon of May 3,” NPS officials said in a news release.

The temperatures on the upper slopes of Denali have been extremely cold over the past week, the park service said, hovering between daytime highs of -25 to -30 degrees Fahrenheit.

In total, 13 climbers have died in falls along that traverse, the NPS said. Most of those falls have occurred on the descent.

Denali is located in south-central Alaska.