Apart of the Nanda Devi glacier broke off this morning near Joshimath in Uttarakhand’s Chamoli district, resulting in a massive flood in the Dhauli Ganga river (one of the source rivers of River Ganga) and causing large-scale devastation in the upper reaches of the ecologically fragile Himalayas.

Around 100-150 people are missing following the flash floods, which damaged the Rishiganga Power Project in Tapovan area and have endangered the lives of people living along the banks of Dhauli Ganga. The flooding has also washed away the Joshimath-Malari bridge.

“The actual number has not been confirmed yet,” but 100 to 150 people were feared dead, Om Prakash, chief secretary of Uttarakhand, told Reuters.

A witness reported a wall of dust, rock and water as an avalanche roared down the Dhauli Ganga river valley located more than 500 km (310 miles) north of New Delhi.

“It came very fast, there was no time to alert anyone,” Sanjay Singh Rana, who lives on the upper reaches of the river in Raini village in Uttarakhand, told Reuters by phone. “I felt that even we would be swept away.”

Uttarakhand’s Police Chief Ashok Kumar told reporters more than 50 people working at the dam, the Rishiganga Hydroelectric Project, were feared dead though some others had been rescued. Kumar also said authorities had evacuated other dams to contain the water rushing in from the flooded Alakananda river.

Prime Minister Narendra Modi said he was closely monitoring the situation.

Homes along the way were swept away as the waters rushed down the mountainsides in a raging torrent. There are fears of further damage in human settlements downstream. Many villages along the river have been evacuated and people have been moved to safer areas. An alert has been sounded in neighbouring Uttar Pradesh for areas along River Ganga.

Uttarakhand Chief Minister Trivendra Singh Rawat has appealed to people to not spread rumours through old flood videos.

He said the water level in the Alaknanda, another tributary of the Ganga, is one metre above normal but the flow was reducing gradually. He added that all districts concerned have been alerted and people have been asked not to go near the Ganga.