SIKKIM — A suspected gas explosion triggered a collapse inside an under-construction tunnel at the Teesta hydroelectric project in Sikkim, India, on Monday, July 20, 2026. The explosion was caused by a buildup of methane gas trapped in the rock formations.

The blast occurred at Samardung village, approximately 40 kilometers (25 miles) from the state capital, Gangtok. Twenty-seven people were inside the tunnel at the time of the explosion, and two workers escaped. Six officials from the National Hydroelectric Power Corporation entered the tunnel to assist in rescue efforts and became trapped.

Survivors reported hearing a loud explosion before debris collapsed into the tunnel. Worker Gandura Oraon stated that he and other workers were eating lunch when the explosion occurred and they escaped in a delivery vehicle. "Luckily, we found the vehicle that had delivered lunch to us sometime earlier. We got into it and drove out," Oraon said.

Sikkim Chief Minister Prem Singh Tamang visited the disaster site and stated that the explosion was triggered by a buildup of methane gas. Tamang announced that the state government would constitute a high-level enquiry committee to ascertain the exact cause of the incident. Chief Secretary Ravindra Telang attended a meeting with rescue agency representatives and prioritized identifying the deceased workers.

Rescue teams detected toxic gases including methane, carbon monoxide, and hydrogen sulfide inside the tunnel. "We found toxic gases such as methane, carbon monoxide and hydrogen sulfide inside the tunnel," NDRF official Nitin Kumar said. Rescuers are using specialized breathing equipment to search for survivors due to dangerous air conditions.

NDRF Deputy Commandant Vivek Kumar said the incident occurred 1.5 kilometers inside the tunnel and that visibility was extremely poor due to carbon monoxide. State disaster management official Rajiv Roka said survival chances for the trapped workers were slim. Superintendent of Police Sonam D Bhutia stated that seven victims had been identified, including one from Sikkim and others from West Bengal, Uttarakhand, and Assam.

NDRF officer Mohsen Shahedi stated that the search-and-rescue operation is focused on a specific 200-metre zone where the remaining people are likely located. The Teesta hydroelectric project has a capacity of 500 megawatts and is being developed by the National Hydroelectric Power Corporation (NHPC). The Sikkim government announced an ex-gratia payment of ₹4 lakh (approx. $4,800) per family of deceased workers and ₹50,000 for injured individuals, as per official statements from the state administration.

Dr. Devesh Walia, a geology professor at North-Eastern Hill University, stated that the area contains young rock formations associated with coal-bearing strata where methane and other gases can accumulate. "It is quite possible that methane along with other gases accumulated underground and may have triggered an explosion," Walia said. Rescue teams encountered a water level of 0.76 meters inside the tunnel, complicating body recovery efforts, as reported by Sikkim State Disaster Management Authority officials.