Death toll in Indian tunnel blast rises to 22

At least seven more bodies were recovered from the tunnel of an under-construction hydroelectric project in India's northeastern state of Sikkim, the state government said on Thursday, bringing the death toll from a blast to 22.

The incident took place on Monday at state-owned National Hydroelectric Power Corp Ltd's project on the Teesta river in the village of Samardung.

An explosion in the tunnel, suspected to have been caused by methane trapped in or released from rocks, filled it with dense fumes and toxic gases, trapping 25 workers and officials of NHPC.

"Rescue operations remain in progress, with specialised teams working in close coordination to locate and recover the remaining victims," Sikkim state government said in Facebook post.

Authorities had warned that the survival chances of those trapped were slim.

Rescue efforts were being hampered by mud and water built up inside the tunnel, as well as breathing issues due to the suspected gas leak, the authorities had said earlier this week.

NHPC on Wednesday said it would pay 500,000 Indian rupees ($5,178) in ex-gratia relief to the families of those killed in the incident.