Rescue efforts have stalled as toxic gases prevent teams from reaching 12 construction workers trapped in a tunnel at a hydropower plant in India. The tunnel collapsed following an explosion on Monday, believed to be caused by a methane gas pocket, and has since led to 13 fatalities as of early Wednesday.
India’s National Hydroelectric Power Corporation (NHPC) said in a statement on Tuesday that the explosion was due to “suspected methane gas trapped/embedded in the rocks, resulting in the generation of dense smoke and toxic gases.”
“Our site engineering teams are working round the clock in coordination with the authorities to stabilize the tunnel environment and ensure rescue operations,” the statement continued.
The blast ripped through a tunnel in India’s northeastern state of Sikkim, effectively stopping work on the 500-megawatt Teesta Stage-VI hydroelectric project in the Namchi district, near the border with China. Two laborers were able to escape after the blast, according to the Associated Press, which cited unnamed officials.
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NHPC said that a rescue response was promptly launched; however, six officials who entered the tunnel to assist with rescue efforts also became trapped, according to the Associated Press.
The company confirmed Tuesday that a total of 25 workers were trapped when the disaster occurred, and 10 people lost their lives in the incident. However, the death toll has since risen to 13, according to a statement from the Sikkim government on Facebook.
On the scene, local reporters interviewed NDRF Deputy Commandant Vivek Kumar, who said that the incident occurred 1.5 kilometers, or almost 1 mile, into the tunnel.
“Carbon monoxide has been detected inside, and visibility is extremely poor. Our team has been carrying out search-and-rescue operations since 5 p.m. yesterday,” Kumar said Tuesday.
But officials at the site explained that the gas exposure is dangerous, and rescue teams can only enter the disaster site for shifts of about 15 minutes at a time—dramatically slowing progress.
The delays followed inclement weather in the region on Monday night, which also set back the immediate rescue efforts, according to police superintendent Sonam Doma Bhutia.
Sikkim’s Chief Minister Prem Singh Tamang, who was present at the site in the explosion’s aftermath, emphasized that the accident was triggered by a build-up of methane gas, although he said there would be a formal investigation.
“The State Government will constitute a high-level enquiry committee to ascertain the exact cause of this unfortunate incident,” he said on social media on Tuesday, adding that the families of the deceased workers would also receive “ex gratia” assistance—referring to gestures made out of goodwill that do not imply obligation or fault.
Tamang also conferred with state officials on Tuesday to review the status of the operation. Chief Secretary Ravindra Telang was part of the meeting, which was also attended by rescue agency representatives, members of law enforcement, and senior officials from the contractor responsible for the site, Patel Engineering.
Telang prioritized identifying each of the deceased, saying that “where identification proves challenging, assistance should be sought from fellow workers and colleagues who are best placed to recognise the victims,” according to a government statement on Facebook.
He also recommended using the oxygen supply “judiciously” to optimize rescue efforts.
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NHPC said in its statement that it is making “every possible effort” to rescue those who remain trapped. On Wednesday, that included pumping water out of the tunnel.
"The recovery of the remaining bodies will commence once the accumulated water has been successfully drained and the site is deemed safe for further operations," according to a statement on Facebook from the Sikkim government.
Tunneling for infrastructure projects in India’s Himalayan region is notoriously risky. The mountains are full of “weak, unstable” rock formations with elevated seismic activity, compromising tunnel stability and safety, according to the International Journal of Environmental Sciences.
At least 18 people died in a coal mine explosion in February in Meghalaya, a neighboring state to Sikkim. In November 2023, 41 construction workers in Uttarakhand were trapped in a collapsed tunnel after a landslide for 17 days before they were rescued.
