Guwahati: Nepal faces the risk of a second flash flood after debris from an ice-rock avalanche formed a temporary dam at a river confluence, the International Centre for Integrated Mountain Development (ICIMOD) said.

The debris is accumulating at the confluence and holding back water, raising the possibility of another flash flood in the valley as more water collects over the next three days, according to ICIMOD.

The temporary lake could also breach gradually and release water without triggering another flash flood, it said.

The warning came as Nepal remained on alert following devastating flash floods along the Nepal-China border. The Nepal Police reported a death toll of 538 on Friday, with more than 1,400 people still missing, including hundreds of foreigners.

Flood risks are expected to remain until two lakes upstream of the flood zone have fully drained. One of the lakes began overflowing on Friday, according to Nepal’s Disaster Management Authority.

The Nepal Police issued a fresh alert after receiving information that a water dam on the Tibetan side had burst again. Chinese state broadcaster CCTV also reported that a dammed lake upstream of the Gyirong border port had begun to overflow.

ICIMOD is investigating whether an ice-rock avalanche at a high-altitude site triggered the initial floods. Its assessment describes the event as a detachment of bedrock beneath a glacier that collapsed into the valley.

The assessment is consistent with the earlier finding that a glacier collapse triggered the initial mudslides and floods along the Nepal-China border.

China’s Foreign Ministry said on Friday that a preliminary assessment indicated that the collapse of a high-altitude glacier in Nepal was behind the mudslides and floods.

Chinese authorities said 555 tourists had been evacuated from Gyirong county in Tibet. They had confirmed five deaths and said more than 558 people remained missing as of Friday.

Meanwhile, Nepal Prime Minister Balendra Shah and his Council of Ministers decided to contribute a month’s salary to the Prime Minister’s Disaster Relief Fund following the floods.

Nepal’s Foreign Ministry said the country did not require assistance from other countries for search and rescue operations.

The cryosphere refers to parts of the Earth’s surface covered by frozen water.