New Delhi, Aug. 26 -- A massive flash flood originating from the Tibet-Nepal border on Wednesday has raised concerns over a possible surge in the Gandak river in Bihar, prompting authorities in the state to step up preparedness in the vulnerable districts.

The flash flood struck the Bhote Koshi river in Nepal's Rasuwa district around 9am and swept away homes, roads, bridges and hydropower infrastructure. The Bhote Koshi and Trishuli rivers, key tributaries of the Narayani-Gandak river system, have witnessed sharp rises in water levels, triggering extensive damage across northern Rasuwa district in Nepal.

Media reports suggest close to 100 people have lost their lives in Nepal, with hundreds missing, including 105 Indians.

The sudden di...