All 25 people trapped in northeastern India tunnel blast die

All 25 people trapped in a tunnel following a blast in northeastern India have died, officials said Thursday.

The 25 people were trapped Monday in an under-construction tunnel at a hydroelectric project in Namchi district of Sikkim state after a "sudden burst of suspected methane gas present inside the rocks, which led to an explosion generating dense fumes and toxic gases," according to state-owned National Hydroelectric Power Corporation (NHPC).

Of those trapped, 19 were workers from Patel Engineering Limited, the statement said.

Authorities said Thursday that the “extensive search” and rescue operation had concluded, “after four days of relentless efforts by multiple rescue agencies.”

“Tragically, all 25 individuals lost their lives, and their bodies were recovered during the course of the operation,” the statement said.

Authorities said preliminary findings suggested that the “blast may have been caused by the leakage of combustible gas”, although the “exact cause will be confirmed following a detailed expert investigation.”