There are grave fears for an Australian tourist reportedly among the 291 foreign tourists missing in massive flash floods that have swept through parts of Nepal on Wednesday, which have already left at least 22 people dead.

That number is expected to rise in the wake of the flood disaster in Rasuwa, just north of Nepal’s capital Kathmandu, which was triggered by an avalanche of ice and rock.

Officials said 384 tourists, including 291 from countries including India, the United States, the United Kingdom and one person from Australia, were reported missing as a result of the flash flood.

The BBC reports that according to the Nepal Tourism Board, the missing foreign nationals include 12 UK nationals, 105 Indians, 37 non-resident Indians, 17 Malaysians, four South Africans, three Americans, one Australian tourist and one Dutch person. There are also efforts to find 93 missing Nepalese nationals.

Search operations on both sides of the border between Nepal and China, which also suffered significant damage, have so far resulted in the rescue of 88 people, according to the Nepalese army.

“We have asked both India and China to help us with the rescue efforts,” said Sasmit Pokharel, a spokesperson for the Nepali government.

The Bhotekoshi River flooded around 9am Wednesday shortly before dozens of multistoried buildings, trucks, and vans were buried under vast quantities of mud in the district of Nuwakot, one of the worst-affected areas. Officials warned residents in several of Nepal’s districts and asked them to stay away from the banks of the Bhotekoshi, Trishuli, and Narayani rivers.

Nepal tourism board officials said most of the missing were likely tourists from India and the Indian diaspora on pilgrimage to Mount Kailash in the Chinese autonomous region of Tibet, a sacred site for Hindus.

South Korean government officials said their citizens working on building a hydropower plant in Nepal were among those reported missing.

Malaysia’s Foreign Ministry also said its embassy in Kathmandu has received reports from travel agencies that they had lost contact with 11 Malaysians believed to be in the Rasuwa district, which was hit hard by the floods.

Meanwhile, Chinese authorities were conducting large-scale search and rescue operations in the Tibetan border area of Gyirong, according to state broadcaster CCTV. Authorities didn’t announce any numbers of dead or injured.

Chinese President Xi Jinping ordered authorities to step up the efforts for people missing after the mudslide, state news agency Xinhua reported. Xi also called for residents at risk to be evacuated from any area on the Chinese side.

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 in a social media post.

The worst-affected area, Rasuwa district, witnessed similar flash floods to those in August last year, when a glacial lake in neighboring Tibet overflowed as a result of high temperatures in the mountain region. Nine people lost their lives and critical infrastructure including a bridge connecting the two countries were damaged at the time.

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

The Lhende Khola River, a tributary of the Bhotekoshi River, witnessed maximum flooding Wednesday, they said.

“The Lhende Khola has flooded twice in fourteen 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.

“In a warming Himalaya, early warning is the first line of adaptation,” he added.

The Himalayan region, which crosses Nepal and several nearby countries including India, is especially vulnerable to heavy rains, floods and landslides because the area is warming up faster than the rest of the world due to human-caused climate change. Research has shown that extreme weather events including heat waves, heavy rains and melting glaciers have become more frequent in the region.

Researchers at the Kathmandu research group 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.