Around 125 people were missing in northern India after a Himalayan glacier broke and swept away a small hydroelectric dam on Sunday, with floods forcing the evacuation of villages downstream.

A wall of dust, rock and water hit as an avalanche roared down the Rishiganga valley deep in the mountains of Uttarakhand, a witness said.

“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, told Reuters by phone. “I felt that even we would be swept away...