Massive flash floods and mudslides in Nepal and Tibet have killed at least 98 people and left hundreds missing, authorities said on Wednesday.

Nepal’s prime minister’s office reported at least 95 deaths. China’s state broadcaster CCTV said a mudslide in Gyirong County, Tibet, killed at least three people and left 265 others missing.

The Bhotekoshi River flooded at around 9 a.m. on Wednesday. The flood destroyed several villages, roads, and hydropower projects, according to Nepali officials.

Authorities issued warnings to residents in several districts. They urged people to stay away from the banks of the Bhotekoshi, Trishuli, and Narayani rivers.

Hundreds of people remain unaccounted for. Nepal Tourism Board official Sunil Sharma said 403 people, including 341 foreign nationals, were reported missing.

Those missing include 133 people from India who were travelling on a pilgrimage to Mount Kailash in Tibet. The list also includes 47 people from the United States, 34 from Australia, and 33 from Britain.

Sharma also reported that 24 Canadian citizens were missing. At least 62 Nepali citizens were also unaccounted for while trekking near Gosaikunda Lake in Rasuwa.

Nepal police said at least 28 police officers were missing.

Security footage from the Chinese side of the Nepal-Tibet border showed people fleeing before a wall of rock, mud and water swept through the area. Buildings and vehicles were destroyed.

Images from Nepal’s hard-hit Nuwakot district showed buildings, trucks and vans buried under large amounts of mud.

Nepal has asked India and China to assist with rescue efforts. Chinese authorities have launched large-scale search and rescue operations in the affected Tibetan border area.

Indian Prime Minister Narendra Modi also offered humanitarian assistance. He said Indian teams were closely coordinating on rescue and relief efforts.

Climate experts at the International Centre for Integrated Mountain Development said an ice and rock avalanche from a glacier on the Nepal side likely triggered the flash flood.

The Lhende Khola River, a tributary of the Bhotekoshi River, experienced the most severe flooding, according to the research group.