Three members of a Latvian climbing expedition lost their lives during an accident on Mount McKinley, located in Alaska’s Denali National Park, as reported by the Latvian Mountaineering Association. A fourth climber was rescued and remains in critical condition.

Mount McKinley, known as Denali, stands at 20,310 feet above sea level, making it the highest peak in North America. The tragic incident took place at approximately 18,000 feet on Wednesday, according to the U.S. National Park Service. A rescue operation ensued on Thursday, despite challenging but improving weather conditions.

On Friday morning, the Latvian Mountaineering Association identified the deceased climbers as Inese Pučeka, Vija Olte, and Renārs Kunigs-Salaks. Mārtiņš Bilzēns was critically injured and transported to the hospital. The Park Service has yet to confirm the fatalities or the climbers’ identities.

The name Denali, the Alaska Native name for the peak, was reinstated last year after having been renamed to honor former U.S. president William McKinley, who never visited the mountain and was assassinated in 1901.

The main climbing season on Mount McKinley generally stretches from late April to mid-July. Most climbers join small, guided expeditions, and about 90% attempt to ascend via the West Buttress route. The Park Service indicated that there were over 500 climbers on the mountain at the time.

The accident became public knowledge on Thursday. The Park Service detailed that four members of a seven-person expedition fell in the Denali Pass region. Of the seven-member group, three climbers managed to return to high camp on Wednesday night following a rescue attempt.

Denali Pass, located at 18,200 feet, lies between the last high camp at 17,200 feet and the summit. This steep, icy section is notorious for its danger, where climbers typically secure themselves to fixed pickets set at intervals of roughly 90 feet.