Sikkim tunnel blast kills at least 10, 17 still missing at NHPC Teesta hydropower site
At least 10 dead and 17 missing after the Sikkim tunnel blast at NHPC’s Teesta hydropower project; rescuers struggle with toxic gases and unstable conditions
Strong summary of the incident
At least 10 people have been confirmed dead and 17 remain missing after a suspected gas explosion caused the collapse of a tunnel under construction at a 500-megawatt NHPC hydropower project in Sikkim. The Sikkim tunnel blast occurred on Monday at Samardung village, close to the Bhutan and Tibet borders, trapping dozens of workers and rescue personnel beneath rubble and inside hazardous air. Authorities said the explosion followed a sudden burst of gas, suspected to be methane, embedded in fractured rock within the tunnel.
Casualties and those still unaccounted for
Local police and company officials confirmed the recovery of 10 bodies while warning that 17 people are still feared trapped. Among the missing are six NHPC officials who entered the tunnel to assist with immediate rescue efforts and did not return, police said. Families of workers have gathered near the project site seeking information, and officials have provided limited details as rescue teams continue operations.
Project location and construction details
The tunnel is part of a 500-megawatt hydropower scheme on the Teesta River being developed by the state-owned National Hydroelectric Power Corporation. The site at Samardung village sits in a remote Himalayan corridor near Sikkim’s border with Bhutan and the Tibetan plateau, an area known for steep terrain and complex geology. Multiple contractors and private crews were reported to be working on tunnelling and construction inside the mountain when the blast occurred.
Suspected cause and hazardous gases detected
NHPC officials and responders said a sudden release of gas trapped in rock pockets is the suspected trigger for the blast, with methane identified as a likely source. National Disaster Response Force (NDRF) teams reported detecting methane along with carbon monoxide and hydrogen sulphide inside the tunnel, complicating entry and search operations. Toxic and combustible gases in fractured Himalayan rock can accumulate in enclosed spaces, raising the risk of explosive bursts during excavation.
Rescue challenges and emergency response
Rescue teams, including NDRF specialists, have been using breathing apparatus and specialised equipment as they contend with dangerous air quality and unstable tunnel sections. Officials described progress as slow due to the presence of toxic gases and the risk of further collapses, forcing teams to adopt cautious, staged clearing procedures. Local police and NHPC personnel remain on site coordinating logistics, while additional technical teams have been summoned to provide shoring, ventilation and gas monitoring.
Regional risks and safety concerns for tunnel projects
Experts note that Himalayan tunnelling carries pronounced risks because of young, heavily fractured rock formations and frequent seismic activity that create voids and gas pockets. Construction accidents in mountain tunnels are a recurring hazard across India’s northern and northeastern states. Authorities recalled a 2023 incident in Uttarakhand where 41 workers were trapped after a tunnel collapse, highlighting chronic safety and geological challenges in large hydroelectric projects.
Investigation and next steps by authorities
NHPC and state officials said a formal investigation will be launched to establish the precise sequence of events, the origin of the gas, and whether procedural lapses contributed to the blast. Forensic teams and engineers are expected to examine drilling records, ventilation logs and monitoring data as part of the probe. In the near term, rescue agencies will prioritize detection and extraction of any remaining survivors while maintaining safety measures to prevent secondary incidents.
Rescue operations at the Teesta project are ongoing under difficult conditions, with officials urging patience as equipment and safety preparations are put in place to allow safer access. Families and local communities remain on site awaiting news, while authorities balance the urgency of searching for survivors against the need to protect rescue personnel from further danger.