The deadly mudslide that swept through a major China-Nepal border crossing was triggered by a high-altitude glacier collapse in Nepal, China's Ministry of Natural Resources said on Thursday, highlighting the growing risks posed by unstable mountain environments as the climate warms.

　　The disaster occurred on Wednesday morning on the Nepal side of the border, sending a torrent of ice, rocks and debris toward Gyirong Port in Gyirong county, a major land crossing linking China and Nepal in Shigatse, Xizang autonomous region.

　　The disaster caused heavy casualties and left hundreds missing in China and Nepal.

　　According to the ministry, the disaster began with a high-altitude glacier collapse in Nepal. The falling ice and rock traveled rapidly down a mountain slope, scouring loose glacial debris along its path and developing into a debris flow before entering the Gyirong Zangbo River and becoming a mudslide.

　　The flow then struck facilities at Gyirong Port before continuing downstream toward Nepal, said Guo Zhaocheng, director of the geological disaster investigation and monitoring center at the China Aero Geophysical Survey and Remote Sensing Center for Natural Resources.

　　The debris flow generated by the glacier collapse traveled at about 50 meters per second. The extreme speed left people little time to react and allowed the flow to affect an area more than 20 kilometers from its source, contributing to the heavy losses, the ministry said.

　　The combination of ice, water, loose rock and steep slopes can make high-altitude disasters particularly fast-moving and difficult to predict, experts said.