India, July 22 -- A tunnel accident at the under-construction 500 MW NHPC Teesta Stage VI Hydroelectric Project in South Sikkim has claimed the lives of 12 workers, while 13 others remain trapped even as rescue operations continue under hazardous conditions, officials said on July 22, 2026.

The incident occurred on July 20 inside the project's ADIT-3 tunnel at Samardung in Namchi district, when a suspected methane gas burst filled the tunnel with dense smoke and toxic gases, trapping 25 workers inside. While NHPC and the Sikkim government have attributed the incident to a suspected methane gas burst, officials said the exact cause will be established after a detailed inquiry.

"The rescue operation is still going on. Twelve bodies have b...