At least seven workers have been killed and more than a dozen remain trapped after a tunnel collapsed at an under-construction hydroelectric project in India’s northeastern state of Sikkim. The incident occurred on Monday afternoon in the Samardung area of Namchi district, where a state-run power corporation was excavating a tunnel for the Teesta Stage VI scheme. Local officials say a suspected build-up of methane gas deep inside the tunnel ignited, triggering a landslide that sealed the entrance and cut off escape routes.

Official casualty figures remain in flux. The district administration initially confirmed seven fatalities, while the state’s disaster management director later told international agencies that nine bodies had been recovered. Some Indian media, citing the chief minister’s office, reported eight dead, and a district magistrate told The Hindu the toll had reached ten. The number of workers still unaccounted for is equally uncertain: estimates from various authorities range from 15 to 27, with the project’s general manager suggesting around 25 people, including officials, were inside at the time of the blast. Rescue teams have not yet been able to verify the exact figure, as hazardous conditions prevent a full headcount.

Rescue operations are being led by the National Disaster Response Force, alongside state disaster units, police, and fire services. Their work has been severely impeded by the continued presence of methane gas and low oxygen levels inside the tunnel, which caused several first responders to lose consciousness. Only personnel equipped with oxygen apparatus and protective suits are permitted to enter, and a specialist team experienced in mining accidents has been flown in from neighbouring West Bengal. The bodies recovered so far have been transported to hospitals in Singtam, Gangtok, and Namchi.

The cause of the explosion is under investigation. Officials in Sikkim have described it as “most probably natural,” pointing to methane leaking from underground rock formations disturbed by the excavation. The region has experienced heavy monsoon rains in recent days, though no direct link to the blast has been established. The incident has drawn attention to the risks of large-scale infrastructure in the seismically active and ecologically fragile Himalayas, where a similar tunnel collapse in Uttarakhand in 2023 trapped 41 workers for 17 days. The rescue operation in Namchi is ongoing, and authorities say a clearer picture of the toll and the number of trapped will emerge only once teams can safely reach the deeper sections of the tunnel.