GUWAHATI: At least 20 people were killed and five others remained trapped inside an under-construction tunnel in Sikkim’s Namchi district collapsed after the sudden release of suspected methane gas led to an explosion, triggering dense smoke and toxic gases.
“An unfortunate incident occurred on July 20, 2026, at 1:04 pm inside the Head Race Tunnel under construction at Samardung in South Sikkim for the NHPC Teesta Stage-VI Hydroelectric Project, due to the sudden explosive release of suspected methane gas trapped/embedded in the rocks, resulting in the generation of dense smoke and toxic gases,” the NHPC said in a statement on Tuesday.
The NHPC said 25 personnel were inside the tunnel. Namchi Deputy Commissioner Anupa Tamling told this newspaper that 12 of them died and efforts were on to rescue the rest. Some reports put the toll at 20.
The NHPC said the project team was working in close coordination with the district administration, National Disaster Response Force, State Disaster Response Force, local authorities and other emergency agencies to support the rescue operations. In addition, a special rescue team from DG Mines-Safety reached the site.
Prime Minister Narendra Modi spoke with Chief Minister Prem Singh Tamang over the phone to enquire about the situation and offered every possible support for the rescue efforts, a Sikkim government statement said.