Eight dead, several trapped after methane explosion triggers tunnel collapse at NHPC project in Sikkim

At least eight people were killed and several others remained trapped after a methane gas explosion triggered a landslide inside an under-construction tunnel of the NHPC Teesta Stage-VI hydropower project in Sikkim on Monday, July 20, officials said.

According to the latest official information released by the district administration on July 21, eight bodies have been recovered and shifted to Singtam District Hospital, STNM Hospital in Gangtok, and Namchi District Hospital.

The incident occurred around midday when methane gas, which had reportedly accumulated in a section of the tunnel about 1.5 km from the entrance, exploded during an attempt to release the trapped gas. The explosion triggered a landslide inside the tunnel, blocking the exit route and trapping workers.

Several workers managed to escape immediately after the blast. However, officials said at least 25 workers were believed to have been trapped inside the tunnel, though the exact number was still being verified.

Namchi Deputy Commissioner Anupa Tamling said the figure of trapped workers had been revised from an earlier estimate of 17 following preliminary verification.

"The figure has been revised based on preliminary verification. The number may still change as authorities continue cross-checking details with company officials and verifying the attendance records of workers present at the site," Tamling said.

Rescue efforts have been severely hampered by hazardous conditions inside the tunnel. Initial attempts by personnel from the Rangpo Fire and Emergency Services were suspended because of dangerously low oxygen levels and the presence of methane gas, with some rescuers reportedly falling ill during the operation.

Teams of the National Disaster Response Force (NDRF) later attempted to enter the tunnel but were also unable to proceed because of the high concentration of gas and unstable conditions caused by the landslide.

The Namchi district administration said rescue operations were being carried out jointly by the NHPC, State Disaster Response Force (SDRF), National Disaster Response Force (NDRF), Sikkim Police, Fire and Emergency Services, the Health Department, and other line departments.

Senior officials from the district administration, NHPC, police and disaster response agencies remain at the site, where efforts are focused on improving ventilation inside the tunnel and identifying the safest route to reach those trapped.

The Sikkim State Disaster Management Authority (SSDMA) said it was closely monitoring the situation and that further updates would be issued as more information became available.