Construction accidents are not uncommon in India, where rapid infrastructure growth often collides with fragile geology, construction lapses, extreme weather and safety standards.
In the Himalayan region, fragile mountains, seismic activity and unpredictable underground conditions make tunnel projects especially risky. An explosion inside a coal mine in neighbouring Meghalaya state in February killed at least 18 workers. In 2023, a tunnel section in northern Uttarakhand state collapsed, trapping 41 workers for 17 days before they were rescued.
Experts say the Teesta River basin, where the hydropower project is being built, lies in a seismically active region marked by young, fragile rock formations riddled with fractures and underground pockets that can trap ancient gases.
Dr Devesh Walia, a geology professor at North-Eastern Hill University in Meghalaya, said the area contains relatively young rock formations, some associated with coal-bearing strata.
“It is quite possible that methane, along with other gases, accumulated underground and may have triggered an explosion,” he said.