At least 18 people have been killed and nearly 400 people remain unaccounted for after a devastating flash flood and mudslide swept through Nepal’s northern Rasuwa district along the Tibet border, destroying villages, roads, bridges and hydropower infrastructure.

The disaster struck early Wednesday along the Bhote Koshi River, which flows from Tibet into Nepal. The full scale of the destruction remained unclear as rescue teams struggled to reach some of the worst-hit areas because roads and communications had been damaged.

The latest reports indicate that 384 travelers — including 291 foreign nationals and 93 Nepali citizens — have lost contact with authorities, according to the Nepal Tourism Board. Many were traveling toward Tibet for the Kailash Mansarovar pilgrimage.

Nepalese authorities have mobilized the army, police and other security forces for search-and-rescue operations. Earlier reports said dozens of people had been rescued, while the number of casualties continued to rise as teams reached previously inaccessible areas.

Initial reports suggested the flood may have been triggered by an earthquake that caused an avalanche, sending large amounts of melted snow and debris into the river.

More recent assessments indicate that an ice-and-rock avalanche or landslide may have blocked a river before suddenly releasing a huge volume of water downstream. The exact cause, however, has not yet been conclusively established.

The sudden surge devastated settlements around Timure and Syaphrubesi in Rasuwa. Roads and bridges connecting the region to the Rasuwagadhi border crossing were damaged, while markets, security posts, customs facilities and hydropower projects were also affected.

The disaster has raised particular concern over foreign tourists and pilgrims who were in the region when the flood struck.

The Nepal Tourism Board said 291 foreign nationals and 93 Nepali travelers were reported missing or out of contact. The group includes people from India, the United States, the United Kingdom, Malaysia, South Africa and other countries.

Indian nationals account for a significant portion of those unaccounted for. Reports indicate that more than 100 Indians are among the missing, including pilgrims traveling as part of the Kailash Mansarovar Yatra.

At least three U.S. nationals and one Australian were also reported among those missing, according to information compiled from Nepalese authorities and travel agencies.

Videos and aerial images from the affected areas showed powerful torrents carrying mud and debris through settlements, while bridges, buildings and vehicles were swept away or buried.

Authorities have warned communities downstream of the Bhote Koshi and Trishuli rivers to remain away from riverbanks and move to safer areas because water levels could rise further.

The disaster has also disrupted electricity generation. Several hydropower projects in the region suffered damage, adding to concerns about infrastructure losses in one of Nepal’s key mountainous energy-producing areas.

The disaster has affected both sides of the Nepal-China border.

On the Tibetan side, a major mudslide struck the Gyirong area near the Nepal border crossing. Chinese authorities reported significant damage and feared substantial casualties. More than 500 rescue personnel were reportedly deployed to assist with emergency operations.

The cross-border impact has complicated rescue efforts, with damaged roads and infrastructure restricting access to several affected locations.

Nepalese security forces have deployed helicopters and rescue teams to search for missing people and evacuate survivors. However, dangerous weather, damaged roads and the continuing threat of flooding have made operations difficult.

Authorities have also appealed to residents along downstream waterways to remain vigilant as emergency teams assess the possibility of further flooding.

The scale of the missing-person reports means the death toll could rise significantly as rescue teams gain access to isolated communities and establish contact with travelers and residents.

The disaster is among the most serious recent floods to hit Nepal’s Himalayan border region and has highlighted the vulnerability of communities and critical infrastructure in the mountainous areas connecting Nepal and Tibet. (ILKHA)