New Delhi, July 23 -- The death toll in the NHPC tunnel collapse in Sikkim's Namchi district rose to 22 on Wednesday, with rescue teams continuing a round-the-clock operation to locate at least three more people believed to be trapped inside the under-construction tunnel.

The incident occurred on Monday inside the seven-km-long head race tunnel (HRT) of the Teesta Stage-VI Hydroelectric Project, when a pocket of methane gas trapped in the rock strata reportedly burst, triggering an explosion that generated intense heat, flames and toxic fumes.

"So far, we have been able to retrieve 22 bodies. If there were 25 people inside the tunnel, then around three are still inside. The rescue operation is going on 24x7," Namchi Superintendent of Po...