10 killed, 17 missing after suspected gas explosion triggers Sikkim tunnel collapse

At least 10 workers were killed and 17 remain missing after a suspected gas explosion caused a tunnel collapse at the Teesta hydropower project in Sikkim. Rescue teams face hazardous conditions due to toxic gases while investigations into the cause continue

Guwahati: At least 10 people were killed and 17 others remain missing after a suspected gas explosion triggered a collapse inside an under-construction tunnel at a hydropower project in India’s northeaster Himalayan state of Sikkim, near the Chinese border, officials said on Tuesday.

The blast ripped through the tunnel on Monday at Samardung village, about 40 kilometers (25 miles) from the state capital, Gangtok, where multiple workers were carrying out construction work on the 500-megawatt Teesta hydroelectric project, Anupama Tamling, a civil official in the area, told reporters. Survivors who managed to escape told authorities they heard a loud explosion before debris came crashing through the tunnel, trapping dozens inside, she said.

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As news of the accident spread, six officials from the state-owned National Hydroelectric Power Corporation (NHPC), which is building the project, entered the tunnel to assist in rescue efforts but became trapped themselves, officials said.

“We have recovered 10 bodies so far and 17 others are feared trapped,” local police chief Sonam Dolma told reporters.Rescue teams, including the National Disaster Response Force (NDRF), have been struggling to reach those trapped because of hazardous conditions inside the tunnel, where toxic gases have accumulated.

“We found toxic gases such as methane, carbon monoxide and hydrogen sulphide inside the tunnel,” NDRF official Nitin Kumar told reporters at the scene. He said rescuers were using specialized breathing equipment as they tried to search for survivors amid dangerous air conditions.Construction accidents are not uncommon in India, where rapid infrastructure growth often collides with fragile geology, construction lapses, extreme weather and safety standards. In the Himalayan region, fragile mountains, seismic activity and unpredictable underground conditions make tunnel projects especially risky.

In 2023 a section of a tunnel in northern Uttarakhand state collapsed, trapping 41 workers for 17 days before they were rescued.Experts say the Teesta River basin, where the hydropower project is being built, lies in a seismically active region marked by young, fragile rock formations riddled with fractures and underground pockets that can trap ancient gases.

Dr. Devesh Walia, a geology professor at North-Eastern Hill University in the neighboring state of Meghalaya, said the area contains relatively young rock formations, some associated with coal-bearing strata. “It is quite possible that methane along with other gases accumulated underground and may have triggered an explosion,” he said.