An explosion suspected to be caused by a build-up of methane gas triggered a collapse inside a tunnel under construction at a hydropower project in India’s northeastern state of Sikkim on Monday. Officials confirmed Tuesday that at least 11 people were killed and 14 remain missing.
State Chief Minister Prem Singh Tamang visited the disaster site near the Chinese border, stating that the blast occurred due to accumulated methane gas. The incident trapped at least 27 individuals, including some who had entered the tunnel to aid in rescue efforts following the initial explosion. Two workers managed to escape.
The blast occurred in a tunnel at Samardung village, approximately 25 miles from the state capital, Gangtok. Workers were engaged in construction on the 500-megawatt Teesta hydroelectric project when the incident took place. Survivors reported hearing a loud explosion before debris rained down, trapping dozens inside.
Rescue teams, including the National Disaster Response Force (NDRF), are working to reach the 14 people still trapped. Operations have been hampered by toxic gases and hazardous conditions within the tunnel. "We found toxic gases such as methane, carbon monoxide and hydrogen sulfide inside the tunnel," said NDRF official Nitin Kumar, noting that rescuers are using breathing apparatus.
Adding to the complexity, six officials from the state-owned National Hydroelectric Power Corporation (NHPC), the project's builder, entered the tunnel to assist in rescue efforts and subsequently became trapped themselves.
Construction accidents are a recurring issue in India, where rapid infrastructure development often faces challenges from fragile geology, construction oversights, extreme weather, and varying safety standards. The Himalayan region, in particular, presents heightened risks for tunnel projects due to its unstable mountains, seismic activity, and unpredictable subterranean conditions that can trap gases.
This incident follows a recent tunnel collapse in northern Uttarakhand state in 2023, which trapped 41 workers for 17 days before their rescue. In a separate incident, an explosion in a coal mine in the neighboring state of Meghalaya in February killed at least 18 workers.
Geologists note that the Teesta River basin, where the hydropower project is located, is a seismically active area. The region's geology is characterized by young, fractured rock formations containing underground pockets where ancient gases can accumulate. Experts suggest that the presence of methane and other gases in such conditions could have precipitated the explosion.