An explosion in a tunnel at an under-construction hydroelectric project in Samardung, Sikkim, India, resulted in the deaths of 22 people. The blast, suspected to be caused by methane gas either trapped in or released from surrounding rocks, caused hazardous fumes and gases, trapping 25 workers and officials from the National Hydroelectric Power Corporation (NHPC).

The explosion occurred on Monday at the NHPC’s project located on the Teesta river. As of Thursday, seven additional bodies were recovered, bringing the total fatalities to 22, according to the state government.

Rescue operations are ongoing, with specialized teams working diligently to locate and recover any remaining victims. The Sikkim state government communicated the continuation of rescue efforts via a Facebook post.

Authorities have expressed concerns over the survival chances for the trapped individuals due to the conditions in the tunnel. Ongoing rescue efforts faced challenges due to mud and accumulated water, in addition to breathing difficulties from the suspected gas leak.

NHPC announced an ex-gratia relief of 500,000 Indian rupees (approximately $5,178) for the families of those who died in the incident, as declared on Wednesday.