Indian rescue crews struggled to reach trapped victims on Sunday (IST) after part of a glacier in the Himalayas broke off, releasing a torrent of water and debris that slammed into two hydroelectric plants. At least nine people were killed and 140 were missing in a disaster experts said appeared to point to global warming.

Video from India's northern state of Uttarakhand showed the muddy, concrete-grey floodwaters tumbling through a valley and surging into a dam, breaking it into pieces with little resistance before roaring on downstream. The flood turned the countryside into what looked like an ash-colored moonscape.

More than 2000 members of the military, paramilitary groups and police took part in the search-and-rescue operation, including soldiers expert in mountaineering, working into the night under bright halogen lights, authorities said.

The flood was caused when a portion of Nanda Devi glacier broke off in the morning, releasing water trapped behind it. It rushed down the mountain and into other bodies of water, forcing the evacuation of many villages along the banks of the Alaknanda and Dhauliganga rivers.

A hydroelectric plant on the Alaknanda was destroyed, and a plant on the Dhauliganga was damaged, said Vivek Pandey, a spokesman for the paramilitary Indo Tibetan Border Police. Flowing out of the Himalayan mountains, the two rivers meet before merging with the Ganges River.

People inspect the site near the damaged Dhauliganga hydropower project at Reni village after a portion of Nanda Devi glacier broke off in the northern state of Uttarakhand, India. Photo / AP

Pandey said at least 42 workers were trapped in two tunnels at the Dhauliganga plant. Twelve were rescued from one of the tunnels, while at least 30 others were still stuck inside the other, he said.

An additional 140 workers at the two plants were missing, Pandey said. Surjeet Singh, a police official, said at least nine bodies were recovered.

"Paramilitary forces have gone 150 metres 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.

The floodwaters also damaged houses, 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.

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

"We knew something wrong had happened.

"We could see the fury of the river."

Indo Tibetan Border Police personnel begin rescue work after a portion of Nanda Devi glacier broke off. Photo / AP

Video showed rescuers in camouflage uniforms and bright yellow or red helmets, using ropes to reach victims. A man who was pulled from a muddy hole threw his arms in the air, and rescuers laughed and exulted with him. Rescue workers comforted victims lying in a row of stretchers in the open.

Scientists have long known that global warming is contributing to the melting and the breakup of the world's glaciers.

Anjal Prakash, research director and adjunct professor at the Indian School of Business who has contributed to UN-sponsored research on global warming, said that while data on the cause of the disaster was not yet available, "this looks very much like a climate change event as the glaciers are melting due to global warming".

Uttarakhand Police Chief Ashok Kumar said officials immediately alerted residents in the area and evacuated them to safer places. Downstream, popular tourist spots on the banks of the Ganges were shut, and all boating activities were stopped.

Prime Minister Narendra Modi tweeted that "the nation prays for everyone's safety" in Uttarakhand.

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 communications in many places.

- AP