Indian rescuers drill Himalayan tunnel to look for trapped workers

Indian authorities have began drilling inside a tunnel in the Himalayas in an attempt to rescue more than 35 workers trapped there after a flash flood that destroyed dams and bridges.

Rescue workers have found the bodies of 36 people and some 170 people remain unaccounted for since Sunday's disaster in Uttarakhand state, most of them workers at the Tapovan Vishnugad hydroelectric project and at the smaller Rishiganga dam, which was swept away by the torrent.

While scores are thought to have been washed away as rock and debris surged down the Dhauliganga River, rescue efforts have been focused on saving the workers stuck in a 2.5 km tunnel.

READ MORE: Time running out for workers trapped in tunnel after India glacier disaster

Rising water

After clearing more than 100 metres of mud, rocks and debris, relief workers on Thursday sent water tankers and generators deep into the tunnel to assist in drilling.

An official with the National Disaster Response Force (NDRF) said the number of rescue teams were limited at the tunnel site after river water levels began to surge.

"There was an input from a village that the river upstream was swelling so we sounded an alert. The rescue mission was stopped for about 30 minutes," Swati Bhadoriya, Chamoli District Magistrate, told Reuters.

Relief workers have been drilling inside a 2.5-km- long tunnel connected to the Tapovan project, where slush and water has been so heavy that soldiers have made only halting progress in four days.

Experts have cautioned there could be still be huge amounts of rock, debris, ice and water that could get released due to changes in temperatures.

"Snow melt or rain could trigger a debris flow any moment, probably not of the size of the event on Sunday, but critical for anybody and anything close to the river," said Holger Frey, a senior scientist with the Glaciology and Geomorphodynamics Group (3G) in the geography faculty at the University of Zurich.

Frustrated families

The men are trying to search for signs of life in smaller tunnels and rooms branching off from the main passage, officials said.

Relatives continued to arrive at the site, but five days after the disaster, there was frustration at the lack of progress.

"They are not telling us anything," said Praveen Saini, whose nephew, Ajay Kumar Saini, is trapped in the tunnel.

Another was holding onto hope that his brother had survived after he was able to ring his mobile.

"If his phone survived, maybe he survived," Jugal Kishore said.

It may take days for more bodies to be recovered from under the tonnes of debris and a thick soup of grey mud.

The body of one policeman washed 110 kilometres (70 miles) downstream to a ghat – a riverside cremation ground – near his ancestral village, the Indian Express reported.

Originally thought to be a glacier breaking apart in the country's second highest, Nanda Devi mountain, and crashing into the river, some scientists now say the flood was more likely to have been caused by an avalanche.

"It appears that the event was caused by a very large rockfall from high up the mountainside which picked up lots of snow and ice on the way down and melted these because of the frictional heat created by the rock fall," said Stephan Harrison, professor of Climate and Environmental Change at the University of Exeter in the United Kingdom.

READ MORE: India's Himalayan disaster puts dams, ignored warnings under spotlight