In the aftermath, 19 bodies have been recovered till now, Uttarakhand DGP Ashok Kumar said on Monday. As of this morning, 32 people from the first tunnel and 121 people from the second were missing and rescue operations to recover people still trapped in the tunnels are underway.

A glacial lake burst, a cloud burst or an avalanche, the impact of climate change or “development” — scientists are not sure what triggered the sudden surge of water near Chamoli in Uttarakhand Sunday morning that briefly raised fears of a repeat of the 2013 disaster in the state.

To take stock of the situation, Uttarakhand Chief Minister Trivendra Singh Rawat Monday visited Chamoli district and said that saving lives was their first priority. Speaking to media persons, Rawat said that they would be successful in clearing the entire debris stretch by today evening.

But while GLOF is being considered to be the most likely trigger for Sunday’s event, there are questions surrounding this possibility. “We don’t know of any big glacial lakes in this region. An avalanche is quite common, and there could have been one, but an avalanche on its own would not result in an increase in the flow of water in the river. The water has to come from a source, and as of now, we do not know what this source is,” said Professor H C Nainwal, a glaciologist at the Hemwati Nandan Bahuguna Garhwal University in Srinagar, Uttarakhand. “We would have to visit the area to find out what exactly happened. Till then, we can only speculate,” he said.

In July 2004, a hydro-meteorological disaster caused a landslide killing 16 people in Joshimath, the epicentre of the current disaster. In June 2005, another hydro-meteorological disaster in Chamoli brought a huge quantity of debris and rock boulders down a seasonal stream. 11 people were killed.

Now, a piece of the Nanda Devi glacier has fallen into Dhauliganga river near Raini village, some 25 km from Joshimath in Garhwal Himalayas. The glacier piece created a massive wave of water, mud and rocks downstream damaging two power projects — NTPC’s Tapovan-Vishnugad hydel project and the Rishi Ganga hydel project. Around half-a-dozen bridges were damaged due to the gush of water.

Argha Banerjee, a glaciologist who works at the Indian Institute of Science Education and Research (IISER), Pune, said it was possible that a glacier lake was present in the area but not known to scientists.

“There are hundreds of such lakes all over the place. We know about many of them, but it is possible that there is one that we do not know about. After today’s event, I started looking at the satellite images, and I couldn’t find any glacial lake in that area. But maybe, if we look at higher resolution satellite images, we would find one,” Banerjee said, adding that there are also instances of lakes forming inside the glaciers, which cannot be detected in satellite images.

“But if there are indeed no glacial lakes in that area, then Sunday’s event would seem to be a bit of a surprise,” he said.

By Karishma Gwalani