Photos: Icy flood that killed at least 41 in India's northeast had been feared for years

New Delhi: Hundreds of rescuers dug through slushy debris and fast-flowing, icy water Friday in a search for survivors after a glacial lake overflowed and burst through a dam in India's Himalayan north, a disaster that many had warned was possible for years.

The flood began in the early hours of Wednesday, when water overflowed a mountain lake. It smashed through a major hydroelectric dam downstream and then poured into the valley below, where it killed at least 41 people and forced thousands to flee their homes.

Police said that 22 of the dead were found kilometers (miles) downriver in West Bengal state, while 100 people are still missing. The disaster underscores a climate dilemma that’s pitted local environmental activists who say the dams are too dangerous against authorities who have approved hundreds of new dams in pursuit of a national green energy agenda.

It wasn't clear what triggered the deadly flood, the latest to hit northeast India in a year of unusually heavy monsoon rains. Experts pointed to intense rain, and a 6.2 magnitude earthquake that struck nearby Nepal on Tuesday afternoon, as possible contributors.

But the design and placement of the 6-year-old Teesta 3 dam, the largest in Sikkim state, were controversial from the time it was built as part of an Indian push to expand hydropower energy. Local activists argued that the location was too dangerous and that the dam didn’t include enough safety measures.

A report compiled by the Sikkim State Disaster Management Authority in 2019 had identified Lhonak Lake as “highly vulnerable” to flooding that could breach dams and cause extensive damage to life and property. The dam’s operator, and local agencies responsible for dam safety, did not respond to requests for comment Friday.

A 2016 study found that over a fifth of the 177 dams built close to Himalayan glaciers could fail if glacial lakes burst, including the Teesta 3 dam. “We knew that this was coming,” said Gyatso Lepcha, general secretary of Affected Citizens of Teesta, an environmental organization based in Sikkim. “The same can happen with other dams also,” he wrote in a statement that called for a safety review of all dams in the state.

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 operation in 2017.

Thakkar said authorities failed to apply the lessons from a 2021 dam breach in Himalayan state of Uttarakhand that killed 81 people, allowing an “eerily similar” disaster to occur. India’s National Disaster Management Agency said Friday that it plans to set up early warning systems at most of India’s 56 known at-risk glacial lakes.

In 2021, the Indian federal government passed a dam safety law that requires operators and local governments to plan for emergencies, but the Teesta 3 is not listed as being monitored for safety by India’s chief dam regulator, the Central Water Commission.

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. One soldier was previously reported missing was rescued, and the bodies of seven have been found, state police said.

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. The army said it was providing medical aid and phone connectivity to civilians in the areas of Chungthang, Lachung and Lachen, and local media reported that said the army was erecting temporary bridges to bring food to affected areas.