Sikkim NHPC Tunnel Collapse: 12 Dead, Up to 15 Workers Feared Trapped as Rescue Teams Battle Rain and Gas Risk

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The death toll in the Sikkim NHPC tunnel collapse has risen to 12, while rescue teams continue searching for between 13 and 15 workers who remain feared trapped inside an under-construction tunnel in Namchi district. Heavy rainfall, waterlogging, unstable ground and the threat of gas accumulation have made the rescue operation increasingly difficult.

The incident took place on Monday afternoon at the ADIT-3 adit of the 500 MW Teesta Stage VI Hydroelectric Project at Samardung in Jholungey. A sudden incident inside the tunnel triggered a cave-in, while a landslide blocked the entrance and left workers trapped underground.

According to reports citing ANI, rescue operations resumed on Wednesday after teams recovered 12 bodies from the site. Officials are continuing efforts to locate those still believed to be inside the tunnel.

The scale of the tragedy has brought renewed attention to safety conditions at major infrastructure projects in Sikkim, a state known for its fragile and seismically active terrain. The incident has also raised questions about the risks faced by workers operating deep underground during the monsoon season, when heavy rainfall can quickly destabilise slopes and complicate emergency operations.

Rescue teams face difficult conditions inside and around the tunnel. Rain has caused waterlogging, while the possibility of dangerous gases accumulating underground has forced authorities to take additional precautions before sending personnel deeper into the affected area.

Teams from the National Disaster Response Force, Sikkim Police, Fire and Emergency Services and coal mining specialists are involved in the operation. Chemical and gas assessment teams have also been deployed to examine conditions inside the tunnel and help rescuers determine whether it is safe to proceed.

The rescue effort remains a race against time as authorities work to clear debris and reach areas where workers may still be trapped. The presence of gas and the unstable condition of the tunnel have added another layer of danger to an already complex operation.

How the Sikkim NHPC Tunnel Collapse Happened

The accident occurred at the ADIT-3 adit of the Teesta Stage VI Hydroelectric Project, a major hydropower development in Sikkim. NHPC, according to a report by The Hindu, said the incident followed a sudden methane burst that triggered a cave-in inside the tunnel.

The collapse, combined with a landslide, sealed the tunnel entrance and trapped a large number of workers underground. Initial reports suggested that around 25 to 27 workers could have been inside the tunnel when the incident occurred.

The exact sequence of events and the circumstances that led to the suspected gas release remain under investigation. Authorities have indicated that a special committee will examine the cause of the accident and determine whether any safety lapses contributed to the tragedy.

For the families waiting outside the site, however, the immediate priority remains the rescue operation. The search teams are working under difficult weather and geological conditions as they try to establish contact with those who may still be alive.

Heavy Rain and Gas Threat Complicate Rescue Efforts

The rescue operation has been severely affected by weather conditions in the region. Heavy rain has increased the risk of further landslides and created waterlogging around the site, making it harder for emergency teams and equipment to operate effectively.

Inside the tunnel, rescuers also face the potential danger of gas accumulation. Authorities have therefore deployed chemical and gas assessment teams to monitor the environment before rescue personnel move into potentially hazardous areas.

Such precautions are critical in underground rescue operations. A tunnel damaged by a sudden collapse can become unstable, while trapped gases may pose serious risks to both survivors and rescue workers.

Officials are consequently attempting to balance the urgency of reaching the trapped workers with the need to protect the rescuers themselves. Any further collapse or exposure to toxic or flammable gases could turn the operation into an even greater disaster.

Despite these challenges, rescue teams have continued their efforts. The recovery of 12 bodies has confirmed the scale of the tragedy, while the search for those still missing remains the central focus of the operation.

Sikkim Chief Minister Announces Financial Assistance

Sikkim Chief Minister Prem Singh Tamang announced financial assistance for the families affected by the tunnel collapse.

The state government will provide an ex gratia payment of ₹4 lakh to the families of workers who lost their lives. Injured workers will receive ₹50,000 each, according to the announcement.

Tamang also said that a special committee would be formed to investigate the incident. The committee is expected to examine the circumstances surrounding the tunnel collapse and identify the factors that contributed to the accident.

The investigation could prove important as authorities seek to determine whether the incident resulted solely from geological and environmental conditions or whether construction and workplace safety measures also require scrutiny.

The announcement of compensation provides immediate financial support to affected families, but the larger questions surrounding safety at major construction sites are likely to remain a subject of public discussion.

Prime Minister Narendra Modi Announces Additional Relief

Prime Minister Narendra Modi also spoke with Chief Minister Prem Singh Tamang following the incident and announced additional financial assistance from the Prime Minister’s National Relief Fund.

The families of those who died will receive ₹2 lakh from the relief fund, while injured workers will receive ₹50,000.

The Centre’s assistance comes in addition to the relief announced by the Sikkim government. Together, the measures are intended to provide immediate support to families dealing with the loss of loved ones and to workers recovering from injuries.

However, the financial assistance is only one part of the response. The immediate priority remains the rescue of workers who are still feared trapped and the safe recovery of those who may have survived the collapse.

The tragedy has also placed renewed focus on the responsibility of agencies involved in large infrastructure projects to ensure that workers operate in safe conditions, particularly in regions where difficult terrain and extreme weather can create additional hazards.

Teesta Stage VI Project Under Renewed Safety Scrutiny

The 500 MW Teesta Stage VI project is one of several large hydropower projects being developed in Sikkim. The run-of-the-river project is scheduled for commissioning in 2029 and is expected to contribute significantly to the state’s power generation capacity.

However, Sikkim’s geographical conditions present unique challenges for large infrastructure development. The state lies in a region characterised by steep mountain slopes, fragile geology and significant seismic activity.

These conditions make construction work particularly demanding. Tunnelling and hydropower projects often require workers to operate in complex underground environments, where geological instability, water ingress and gas-related risks can create serious safety challenges.

The latest tunnel collapse is therefore likely to intensify scrutiny of safety protocols at major construction projects across the state.

Experts and authorities may now examine whether existing emergency response systems, underground monitoring mechanisms and evacuation procedures are adequate for projects operating in such difficult terrain.

The incident also highlights the risks that construction workers face while working on large infrastructure projects that often remain far from public view. While hydropower development can bring economic and energy benefits, the safety of workers must remain a central consideration throughout the construction process.

Families Await Answers as Search Operation Continues

As rescue operations continue, the families of the missing workers remain in a state of uncertainty. The recovery of 12 bodies has deepened the tragedy, but the possibility that some workers could still be alive has kept hope alive among relatives and colleagues.

Rescue personnel are continuing to assess the tunnel and work through the debris while monitoring gas levels and other potential hazards.

The operation could take time because rescuers must proceed carefully. Clearing debris too quickly or entering unstable sections of the tunnel without adequate assessment could put additional lives at risk.

At the same time, every hour remains crucial for workers who may still be trapped underground.

The authorities are expected to provide further updates as rescue teams make progress and as investigators gather more information about the circumstances surrounding the collapse.

For now, the Sikkim NHPC tunnel collapse has left 12 people dead, several others injured and up to 15 workers feared trapped. The tragedy has not only triggered a major rescue operation but has also raised serious questions about worker safety, emergency preparedness and the risks associated with large-scale construction in one of India’s most challenging mountain regions.