An American mountaineer and her Nepali guide were killed when avalanches struck high on the Shishapangma mountain’s slopes Saturday as more than 50 climbers were attempting to reach the summit, according to Chinese news agency Xinhua on Sunday.

Shishapangma, the world’s 14th tallest peak, was hit by two avalanches at elevations of 7,600 and 8,000 meters on Saturday, killing US climber Anna Gutu and Nepalese guide Mingmar Sherpa, who were attempting to top the “eight-thousander” mountain.

Another US climber, Gina Marie Rzucidlo, and her Nepalese guide, Tenjen Sherpa, were missing, Xinhua said.

Tenjen Sherpa was the guide for Norway’s Kristin Harila when they climbed K2 in Pakistan in July to become the world’s fastest climbers to scale all 14 peaks over 8,000 metres, Reuters reported,

Had one of the Pakistani climbers, Sirbaz Khan, reached the top of Shishapangma, he would have become the first Pakistani to summit all 14 mountains over 8,000 metres.

Over 300 successful summits of Shishapangma have been recorded, with under 10% of climbers dying in their attempts, compared to a nearly 30% fatality rate for Nepal’s Annapurna I, one of the world’s most dangerous peaks.

Among those who had previously died on Shishapangma was famed American climber Alex Lowe in 1999, also because of an avalanche.

His body as well as the remains of his climbing companion David Bridges were found in 2016 in a partially melted glacier.

October, a popular month for Himalayan climbers due to its stable conditions, is being threatened by global warming, which is increasing avalanche risks in high-altitude regions, according to scientists.

Last week, a Chinese expedition set up a series of weather stations on the 8,201-metre Cho Oyu on Tibet’s border with Nepal to measure the impact of climate change in the Himalayas.