At least 10 workers were killed and more than 18 others are feared trapped after a landslide inside a tunnel under construction triggered a suspected methane gas leak in India's northeastern state of Sikkim, officials said.
So far, 12 workers have been rescued, while search and rescue operations are continuing with teams from the National Disaster Response Force (NDRF) and other emergency agencies.
The incident occurred around 3:09 pm on Monday at the Samardung tunnel in South Sikkim, where Patel Engineering is constructing a section of the Teesta Stage VI Hydroelectric Project.
According to the Chief Minister's Office, rescue efforts are ongoing, although the exact number of workers trapped inside the tunnel has yet to be confirmed.
Preliminary reports suggest that a landslide inside the tunnel blocked the passage, trapping several workers. Rescue operations have been slowed by a suspected methane gas leak, making it unsafe for emergency personnel to reach the affected area.
Alongside the NDRF, teams from the State Disaster Response Force (SDRF), Sikkim Police, and the Fire and Emergency Services have been deployed. Authorities have also restricted traffic around the site to support rescue work.
Namchi District Collector Anupa Tamling said rescue teams from Siliguri and Pakyong, along with the SDRF, were mobilised immediately after the incident was reported.
She said firefighters and police officers tried twice to enter the tunnel without protective equipment but had to retreat because of dangerous conditions.
The first NDRF team later evacuated those emergency workers, while a second NDRF team entered the tunnel to continue the rescue operation.
Officials said methane levels inside the tunnel initially remained so high that rescuers could not reach the area where the trapped workers are believed to be.
Tamling said the exact cause of the landslide is still unknown. According to workers who escaped, they heard a loud blast-like sound inside the tunnel before running to safety.
She cautioned that the number of people trapped remains provisional, adding that the administration's top priority is to rescue everyone safely.
Sources said several members of the first rescue team suffered dizziness and breathing problems after being exposed to methane gas. They were safely brought out and taken to a nearby hospital for treatment.