Ice-cold floodwaters have swept through mountain towns in India’s Himalayan northeast, killing at least 40 people, washing away houses and bridges, and forcing thousands of people to leave their homes.

The flood began shortly after midnight on Wednesday, when the waters of a glacial lake overflowed, cracking open the biggest hydroelectric dam in Sikkim state and then cascading through towns in the valley below.

The Sikkim State Disaster Management Authority said in a statement that more than 2,000 people had been rescued, adding that state authorities set up 26 relief camps for more than 22,000 people affected by the floods.

Rescue workers were still searching for nearly 100 missing people, including 23 soldiers, after the floods also hit several army camps.

Vinay Bhushan Pathak, the state’s top bureaucrat, said that 26 people had been taken to hospitals with injuries, while nearly 3,000 tourists were stranded in the flood-hit areas along with 700 taxi drivers.

It was the latest deadly flood to hit northeast India in a year of unusually heavy monsoon rains. Nearly 50 people died in flash floods and landslides in August in nearby Himachal Pradesh state, and record rains in July killed more than 100 people over two weeks in northern India.