Rescue operations continued at the Samardung Tunnel (Teesta VI) project in North Sikkim after a suspected methane gas leak inside the tunnel on July 20 trapped 25 project personnel, resulting in casualties, according to Patel Engineering Limited (PEL).
The company said the incident occurred at around 1 pm in the Adit-3, Face 4B section of the project. A sudden release of suspected methane gas trapped within the rock formation allegedly triggered a gas burst or explosion inside the tunnel, filling the area with dense fumes and toxic gases and hampering rescue efforts.
PEL said its project team is working closely with the district administration, the National Disaster Response Force (NDRF), the State Disaster Response Force (SDRF), local authorities and other emergency agencies to support the ongoing rescue mission. The company added that all necessary equipment, resources and technical assistance have been deployed, while its site engineering team is working round the clock to help stabilise the tunnel environment and enable rescue teams to safely reach the affected workers.
The company said gas detection checks are part of the project’s established safety protocol, with methane (CH₄), carbon monoxide (CO), hydrogen sulphide (H₂S) and oxygen levels monitored before work begins, including on the day of the incident. A detailed investigation will be conducted to determine the exact cause of the accident.
The incident has drawn widespread attention across Gangtok, where infrastructure and hydropower projects are seen as major contributors to Sikkim’s economy. Industry observers believe the accident could temporarily heighten scrutiny of tunnel safety standards and project execution practices, while businesses and contractors are closely monitoring developments for any potential impact on construction activity, supply chains and investor confidence in the state’s infrastructure sector. PEL said it remains committed to supporting rescue agencies and the affected families during the ongoing operation.