TRISHULI, Nepal: 2,500 people, including more than 700 foreign nationals, are still missing in Nepal and China', as of Saturday, after a massive wall of mud and rock collapsed into a Himalayan river and triggered devastating flash floods earlier this week.

The death toll rose to 538 on Saturday, as rescuers traced the thousands of people still missing.

Rescue teams in Nepal used helicopters to search for survivors and deliver emergency supplies to thousands of people who had been cut off in towns and mountain valleys. The disaster struck on Wednesday along a major road connecting Kathmandu with Lhasa in Tibet. The route is widely used by trekkers, pilgrims and other travellers.

Police and tourism officials said 826 people were still missing in Nepal, including almost 500 foreign nationals.

The missing tourists came from more than 20 countries. They included 290 people from India, 63 from the United States, 41 from Australia, 33 from Britain, 25 from Canada, and nine from South Korea, with these figures being constantly revised.

Malaysia's Foreign Ministry said it had been unable to contact 51 of its nationals who were believed to be in the affected area. However, there was no official confirmation that any Malaysian citizen had been killed or injured.

In Tibet's Gyirong county, 558 people were reported missing, according to Chinese state broadcaster CCTV. The figure included 260 foreign nationals. China said three people had died in the disaster.

Nepal's Prime Minister Balendra Shah travelled by road to one of the worst-hit districts, Nuwakot, to inspect the flood damage, his office said on social media.

The cause of the disaster also became clearer. The U.S. Geological Survey said an earthquake initially reported as magnitude 4.4 was actually seismic energy produced by the collapse of glacial rock and ice. A large debris flow followed the collapse.

Many of those caught in the disaster were pilgrims travelling to Kailash Mansarovar, a high-altitude religious site in Tibet that is considered sacred by Hindus and Buddhists, among others.

Sagar Pandey, chief executive of a Himalayan tourism company, said 15 Indian-Australian pilgrims travelling with his company were among those missing.

The U.S. State Department said it was sending a disaster response adviser to the region and would provide $500,000 in assistance.

Canada was also monitoring the situation closely. Prime Minister Mark Carney described the flooding as "absolutely devastating" in a post on X.

Security camera footage from the Chinese side of the border showed large numbers of people running away from a powerful torrent of mud, rocks and water. The flow destroyed buildings and swept away vehicles.

Indian spiritual leader Jaggi Vasudev, widely known as Sadhguru, said on X that 77 people returning from Mount Kailash with groups organised by his Isha Foundation were at an immigration centre in Gyirong, Tibet, when the flooding began.