The flood was caused when a portion of Nanda Devi glacier broke off in the Tapovan area of the northern state of Uttarakhand on Sunday morning. A video shared by officials and taken from the side of steep hillside shows a wall of water surging into one of the dams and breaking it into pieces with little resistance before continuing to roar downstream.

The Rishiganga hydropower plant on the Alaknanda River was destroyed, while the Dhauliganga hydropower plant on the Dhauliganga River was damaged, said Vivek Pandey, a spokesman for the paramilitary Indo Tibetan Border Police. Flowing from the Himalayan mountains, both rivers meet before merging with the Ganges River.

Pandey said at least 42 workers got trapped inside two tunnels at the Dhauliganga plant. While 12 workers trapped inside one tunnel were rescued, at least 30 others were still stuck inside the other tunnel, he said.

Another 140 workers at the two plants were missing, Pandey said.

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Surjeet Singh, a police official, said nine bodies were recovered so far amid intensified rescue operations that went into the night. Authorities installed halogen lights in the area to continue rescue operations.

“Paramilitary forces have gone 150 meter down in the tunnel to rescue people. The operation is expected to continue until we bring these people out alive,” said Pravin Alok, a spokesman for the State Disaster Relief Force.

There were also houses that were damaged in the flooding, said Ravi Bejaria, a government spokesman, though he had no details on the number and whether any of the residents were injured, missing or dead.

More than 2,000 members of the military, paramilitary groups and police were helping in the rescue operation, Bejaria said. Pandey said soldiers who are experts in mountaineering and rescue operations had been called in.

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“The situation is under control and there is no need for panic,” he said.

Officials said when the glacier broke it sent water trapped behind it as well as mud and other debris surging down the mountain and into other bodies of water. Many villages were evacuated as authorities issued an advisory urging people living on the banks of the Alaknanda and Dhauliganga rivers to move to safer places immediately.

Anjal Prakash, research director and adjunct professor at the Indian School of Business who has contributed to U.N.-sponsored research on global warming, said that while data on the cause of the disaster in not yet available, “this looks very much like a climate change event as the glaciers are melting due to global warming. The impact of global warming on glacier retreat is well-documented.”

Authorities emptied two dams farther down the river to stop the flood waters from reaching towns of Haridwar and Rishikesh, where popular tourist spots on the banks of the Ganges River were shut and all boating activities were stopped.

“It all started sometime around 10 in the morning. We heard a bang, which shook our village,” Dinesh Negi, a resident of Raini village, told The Associated Press by phone.

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He said they watched from their village high above one of the rivers as the water turned muddy and surged in a torrent.

“We knew something wrong had happened,” Negi said. “We could see the fury of the river.”

Uttarakhand police chief Ashok Kumar said officials immediately alerted residents living in the area and evacuated them to safer places.

Prime Minister Narendra Modi in a tweet said he was “constantly monitoring the unfortunate situation.” He added: “India stands with Uttarakhand and the nation prays for everyone’s safety there.”

In 2013, thousands of people were killed in Uttarakhand after heavy rains triggered landslides and floods, washing away thousands of houses and roads and cutting communication links in many parts of the state.