Over 100 people are missing after South Lhonak, a glacial lake in the Himalayas, burst its banks last week, killing at least 70 people, including nine soldiers.

Heavy rains, earthquakes or avalanches can trigger such outbursts, or the sudden release of water from a lake fed by a glacier.

Early warning systems can help authorities evacuate people in time and open dam flood gates downstream to minimise damage.

Indian National Disaster Management Authority (NDMA) revealed after the Sikkim disaster that it had surveyed two at-risk lakes in early September to deploy early warning systems in case of glacial lake outbursts. learned that some early warning work was initiated at South Lhonak, one of the lakes surveyed.

Even so, the flood just weeks later prompted people to question why there was no early warning system already in place, especially since the lake has long been known to be dangerous.