Pakistan, July 23 -- The death toll from a tunnel explosion at an under-construction hydroelectric project in India's northeastern state of Sikkim has risen to 22, after rescue teams recovered seven more bodies from the site, authorities said on Thursday.

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The accident occurred on Monday inside a tunnel at the National Hydroelectric Power Corporation (NHPC) project on the Teesta River in the village of Samardung. Officials believe the blast was likely caused by methane gas trapped within or released from surrounding rock formations, filling the tunnel with toxic fumes and dense smoke.

A total of 25 workers and NHPC officials were trapped inside the tunnel following the explosion. ...