At least 10 workers have been killed and about 15 others remain trapped following a suspected gas explosion inside an under-construction hydroelectric tunnel in India’s northeastern state of Sikkim.Tourist Destinations
The accident occurred at approximately 1:04 pm on Monday, July 20, inside the head-race tunnel of the 500-megawatt Teesta Stage VI Hydroelectric Project at Samardung in South Sikkim’s Namchi district. Twenty-five personnel were reportedly inside the affected section when the incident occurred.
CGTN initially reported that nine people had died and 15 were trapped. State-owned hydropower company NHPC later confirmed that the number of fatalities had risen to 10 as rescue teams continued searching for the remaining workers.
Preliminary reports suggest that a sudden release of gas trapped within the surrounding rock caused an explosion inside the tunnel. The blast generated dense smoke and toxic fumes and may have triggered a landslide that blocked access to part of the underground construction area.
Officials initially suspected methane was responsible for the explosion. However, National Disaster Response Force personnel later said instruments were detecting carbon monoxide inside the tunnel. The exact presence and role of methane had not been conclusively established, and investigators said a detailed examination would be required to determine the cause.Urban & Regional Planning
The dangerous concentration of smoke and poisonous gases has complicated the rescue operation. Emergency crews have been working to ventilate and stabilise the tunnel before moving deeper into the affected section.
Teams from the National Disaster Response Force, State Disaster Response Force, district administration and local emergency services were deployed at the site. Specialists from India’s Directorate General of Mines Safety also joined the operation to assess underground conditions and assist rescuers.
NHPC said senior company officials and engineering teams were present at the project site to supervise the emergency response. The company said personnel were working continuously to make the tunnel safe enough for rescuers and to reach those still trapped underground.
Union Home Minister Amit Shah spoke with Sikkim Chief Minister Prem Singh Tamang to review the situation and assured the state government of full assistance from the central authorities. The state administration and disaster-management agencies were also monitoring the operation.Environmental & Man-Made Disasters
The Teesta Stage VI project is a major hydroelectric development being constructed on the Teesta River. The accident occurred in its head-race tunnel, which is designed to transport water towards the project’s turbines for electricity generation.
Authorities have not yet issued a final explanation for the explosion or confirmed whether construction procedures, geological conditions or safety failures contributed to the disaster.
NHPC said a formal investigation would be conducted to establish the exact sequence of events. The company also said assistance was being extended to the victims’ families and to the agencies involved in the rescue operation.
The tragedy has renewed concern over worker safety in major tunnel and hydropower projects across India’s geologically fragile Himalayan region, where construction teams can face landslides, unstable rock formations and underground gas accumulation.
