When a huge chunk of ice snapped off a glacier and fell into a river in the Himalayas on Wednesday, it unleashed a torrent of water, ice and mud that cut a devastating path through a valley on the border between Nepal and the Tibetan region of China.

The flash flood swept away homes, bridges, schools and hydropower projects, the authorities said. At least 160 people were killed. Hundreds more remained missing, including more than 100 Indians on a pilgrimage and hundreds of foreign tourists, officials said.

Tenzing Chogyal Sherpa, an expert in atmospheric and water processes at Utrecht University in the Netherlands, said the disaster was a “brutal reminder,” given the climate extremes in the valley, that “events like this may happen again.”

The Nepali Army has mobilized rescue and evacuation operations and has set up a makeshift hospital in the flood zone. The death toll is expected to rise.