Rescue teams searched through the muddy devastation Thursday for more than 1,300 people missing along the Nepal-China border after catastrophic floods triggered by a glacier collapse.

The death toll has surged to at least 273 people. Videos of the tragedy showed the torrents of water and mud swallowing up buildings and people on Wednesday.

Hundreds of tourists and pilgrims from more than 30 countries, including the U.S., are among the missing. Many of them were in the area for trekking or a pilgrimage to a sacred Hindu site.

(WATCH: Watch as raging floodwaters snap bridge in half in Nepal)

Experts said an avalanche from a glacier was the likely cause in the warming Himalaya region.

Villages and infrastructure were overwhelmed by the massive flash flood that was triggered at about 9 a.m. Wednesday along the Bhote Koshi River. Residents in multiple districts were warned of the danger and were told to stay away from the Bhote Koshi, Trishuli and Narayani rivers.

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Helicopters deployed for rescue as roads were damaged

The disaster has left at least 270 dead and 826 people missing in Nepal, and three dead and 558 missing in Tibet, authorities said.

(MORE: Manhattan-sized iceberg snaps off glacier in Greenland)

Nepalese officials said that dozens of bridges were destroyed and nearly 40 kilometers (25 miles) of roads were damaged, complicating search efforts.

The Nepalese army has rescued more than 100 people from flood-affected areas through helicopter operations on Thursday morning, army spokesperson Brig. Gen. Raja Ram Basnet said.

At least eight foreign nationals were airlifted to the country’s capital, Kathmandu, he said, adding that army teams also evacuated people trapped inside facilities linked to the Trishuli hydropower project.

Rescuers found bodies hundreds of miles downstream from the disaster zone in Chitwan district. Dozens of injured people have been transported to Kathmandu for advanced medical care.

The region's steep valleys are economic lifelines and travel corridors but precarious ones when disaster strikes. Images showed what appeared to be the second floors of buildings in Nepal's hard-hit Nuwakot district slathered in mud after the torrent rushed by. Debris hung from tree branches and wires, vehicles were buried and some stunned survivors were caked in mud. Many missing were on pilgrimage to a sacred site

The village of Soley in Nuwakot, with about 25 homes, was virtually wiped out, said Nirajan Paudyal, a Kathmandu-based journalist whose parents and other relatives live there. Desperate for information, he traveled to the area on Thursday for news of his family.

"There is no update till now. I fear there won’t be any update,” Paudyal said.

(MORE: A looming rock collapse threatens a Swiss village as thawing permafrost destabilizes the Alps)

Hundreds of foreigners are missing

According to Nepal’s Tourism Board, 517 of the missing people in the country were foreigners and 178 of them were from India, and some were likely there on a pilgrimage to Mount Kailash in Tibet, a sacred site for Hindus.

The site, however, drew tourists from all over the world. More than 60 of the missing in Nepal were from the U.S. and the rest were from 30 other countries, ranging from Ukraine and the U.K to South Africa and Japan, the Tourism Board said.

Indian spiritual guru and the head of the Isha Foundation, Sadhguru Jaggi Vasudev, said on X that 77 people from one of his pilgrimage groups to the Mount Kailash were caught in the flash floods at the immigration office at the Nepal-China border.

A visibly emotional Sadhguru said in a video that the group included foreign nationals from various countries. He said that there was no official information on the whereabouts of those who were at the immigration office, including 22 U.S. nationals.

“Looking at the scale of destruction, it looks bad. The same building where we were for the immigration just a week ago, that entire building is washed away,” Sadhguru said.

In addition, China’s Ministry of Foreign Affairs spokesperson Lin Jian said that nearly 100 Chinese citizens were missing on the Nepal side. He said that according to preliminary information 260 of those missing in Tibet were foreigners.

Experts say glacier collapse caused devastating floods

The U.S. Geological Survey first reported a magnitude 4.4 earthquake early Wednesday, about 66 kilometers (41 miles) north of Kathmandu, near the border.

The USGS later updated its analysis to say the seismic event it measured was a magnitude 5.2 glacier collapse that sent debris flowing downstream with catastrophic impact on communities. It said its determination was based on data from nearby seismic stations, long period seismic waves and satellite imagery, and that no earthquake had occurred.

Countries express alarm over missing citizens

South Korean government officials said nine citizens working on building a hydropower plant in Nepal were among those reported missing. Malaysia’s foreign ministry said its embassy received reports from travel agencies that they had lost contact with 11 Malaysians believed to be in Rasuwa district. Russia’s embassy in Nepal said four citizens reportedly in the affected area were missing.

Indian Prime Minister Narendra Modi spoke with Nepal’s Prime Minister Balendra Shah and offered help. “India is prepared to provide Nepal with all possible types of humanitarian assistance. Our teams are closely coordinating on rescue and relief efforts,” Modi said on social media.

Some United Nations bodies were deploying “in an effort to meet what will clearly be massive humanitarian need,” U.N. spokesperson Stephane Dujarric said.

In a joint statement, Australia, Britain, the European Union, Finland, France, Norway and Switzerland expressed solidarity with people in Nepal, adding: “We encourage all those in affected areas to follow the guidance of local authorities and official safety advisories as the situation continues to evolve.”

The same region saw flash floods last year

Climate experts at the Kathmandu-based International Centre for Integrated Mountain Development said an avalanche from a glacier likely caused Wednesday’s flash flood.

“Hydrological observations indicate the exceptional speed and magnitude of the flood wave,” they said in an emailed statement, noting that water levels at one point on the Trishuli River rose by as much as nine meters (27 feet) over half an hour.

The Lhende Khola River, a tributary of the Bhote Koshi, had maximum flooding, they said.

“The Lhende Khola has flooded twice in 14 months, this time triggered by an ice rock avalanche from a glacier on the Nepal side that blocked the river and released a sudden surge downstream,” said Saswata Sanyal, a disaster risk reduction specialist at the climate research group.

He noted the importance of early warnings in “a warming Himalaya.”

The region saw similar flash floods in August last year, when a glacial lake in Tibet overflowed because of high temperatures. Nine people were killed, and critical infrastructure, including a bridge connecting Nepal and China, was damaged.

The Himalayan region, which spans several countries including India, is especially vulnerable to heavy rains, floods and landslides because of warming due to human-caused climate change. Research shows that extreme weather events, including heat waves, rains and melting glaciers, have become more frequent.

Researchers in Kathmandu found earlier this year that glaciers across the Hindu Kush Himalaya region are melting at an accelerating rate, with ice loss rates doubling since 2000, primarily due to rising global temperatures and climate change.

Information from the Associated Press was used in this report.