Ice-cold floodwaters swept through mountain towns in India’s Himalayan northeast, killing at least 31 people, washing away houses and bridges, and forcing thousands of people to leave their homes, officials said Friday.

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

Also read: Flash floods kill at least 14 in northeastern India and leave more than 100 missing

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, record rains in July killed more than 100 people over two weeks in northern India.

More than 2,000 people were rescued after Wednesday’s floods, the Sikkim State Disaster Management Authority said in a statement, adding that state authorities set up 26 relief camps for more than 22,000 people impacted by the floods.

Also read: Flooding displaces tens of thousands and kills 1 as heavy monsoon rains batter Indian villages

Rescue workers were still searching for nearly 100 missing people, including 22 soldiers, on Thursday, according to the Sikkim state government.

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.

“We are evacuating them through helicopters provided by the army and the air force,” he said.

Also read: New Delhi schools close after monsoon floods kill at least 15, Pakistan on alert for more flooding

The South Llonak Lake has been rising in recent years as a warming climate melts the glaciers that feed it, putting pressure on the dam that contains it, but it wasn't clear what triggered the breach Wednesday. Experts and varying government reports have pointed to sudden, intense rains in the area, and a 6.2 magnitude earthquake that struck nearby Nepal on Tuesday afternoon.

Eleven bridges in the Lachan Valley were washed away by the floodwaters, which also hit pipelines and damaged or destroyed more than 270 houses in four districts, officials said.

Several towns, including Dikchu and Rangpo in the Teesta basin, were flooded, and schools in four districts were ordered shut until Sunday, the state’s education department said.

Parts of a highway that links Sikkim, the state capital, with the rest of the country were also washed away.

The floods also hit several army camps, burying vehicles in feet of mud, according to images released by the Indian military.

The Press Trust of India news agency cited a statement by neighboring West Bengal state as saying that the bodies of four soldiers were found. However, it wasn’t immediately clear whether they were among the 22 missing soldiers, or had died separately.

One soldier who had been reported missing on Wednesday was later rescued by authorities, the army said in a statement.

The army is providing medical aid and phone connectivity to civilians in the areas of Chungthang, Lachung and Lachen in north Sikkim, the army statement said.

Prime Minister Narendra Modi’s office said in a statement that the government would support state authorities in the aftermath of the flooding.

The Teesta 3 hydropower project, built on the Teesta River, took nine years and cost $1.5 billion to construct. The project was capable of producing 1,200 megawatts of electricity — enough to power 1.5 million Indian homes — and began operations in 2017.

Despite risks to dams due to increasing frequency of extreme weather, the Indian federal government aims to increase India’s hydroelectric dam output by half, to 70,000 megawatts, by 2030.

Disasters caused by landslides and floods are common in India’s Himalayan region during the June-September monsoon season. Scientists say they are becoming more frequent as global warming contributes to the melting of glaciers there.

“This is, incredibly sadly, another classic case of a cascading hazard chain that amplifies as you go downstream,” said Jakob Steiner, a climate scientist with the International Center for Integrated Mountain Development, commenting on Wednesday's flash flooding.

Earlier this year, Steiner’s organization published a report saying that Himalayan glaciers could lose 80% of their volume if global warming isn’t controlled.

Lst month, dam breaches caused by Storm Daniel caused devastating damage to the city of Derna in Libya.

In February 2021, flash floods killed nearly 200 people and washed away houses in Uttarakhand state in northern India.