GUWAHATI, India (AP) — A suspected gas explosion triggered a collapse inside an under-construction tunnel at a hydropower project in India’s northeastern Himalayan state of Sikkim, near the Chinese border,

A gas leak was also suspected at the site, hindering the rescue operations.

Incident occurred on Monday in Sikkim, where workers were constructing a tunnel for a state-run hydropower project; official says around 25-27 people trapped.