At least 11 people have died and several others remain missing after a suspected gas explosion triggered the collapse of a tunnel under construction at a hydroelectric project in Sikkim, a northeastern Himalayan state of India near the Chinese border. The incident occurred on Monday at the site of the 500-megawatt Teesta hydroelectric project, located near Samardung village, about 40 kilometers from the state capital, Gangtok.
Officials reported that workers inside the tunnel heard a loud explosion before debris fell, blocking the passage and trapping dozens. Survivors who escaped described the blast, which led to the collapse. In addition to the construction workers, several officials from the National Hydroelectric Power Corporation (NHPC), the state-owned company overseeing the project, entered the tunnel to assist in rescue operations but also became trapped.
Rescue efforts have been hampered by hazardous conditions, including the presence of toxic gases such as methane, carbon monoxide, and hydrogen sulfide accumulating inside the tunnel. Specialized breathing gear is being used by the National Disaster Response Force (NDRF) and other teams to attempt to reach survivors. The presence of these gases has significantly complicated the search and recovery operations.
There are varying reports concerning the number of casualties and missing individuals. Some officials have confirmed the recovery of 10 to 11 bodies, while others cite nine confirmed dead with 14 to 17 still trapped. Authorities estimate that between 25 and 27 people may have been inside the tunnel at the time of the explosion.
The precise cause of the blast remains under investigation. Officials have suggested that it might have been triggered by natural factors, possibly related to underlying methane gas escaping from rock formations deep within the tunnel. Recent heavy monsoon rains in the region could have also contributed to unstable conditions.
A specialized rescue team with expertise in mining accidents has been deployed to support ongoing operations. The situation parallels previous incidents in the fragile Himalayan region, where large infrastructure projects have faced challenges due to difficult terrain and environmental sensitivities. In 2023, for example, 41 workers were rescued after being trapped for more than two weeks under a collapsed road tunnel in Uttarakhand, another mountainous Indian state.
Authorities continue their efforts to reach survivors and assess the full impact of the accident, which underscores the risks associated with large-scale construction in remote and geologically complex areas.