Tunnel collapse in India kills at least 12 workers

At least 12 people were killed and some remain missing after a suspected gas explosion triggered a collapse inside an under-construction tunnel at a hydropower project in India's northeastern Himalayan state of Sikkim.

The blast ripped through the tunnel on Monday with 21 labourers working inside on the 500-megawatt Teesta hydroelectric project. Several power utility officials entered the tunnel to assist rescue, but became trapped themselves.

12 bodies were recovered and 13 people were believed to be still trapped. Local authority said the blast was believed triggered by a buildup of methane.

Rescuers struggled to reach those trapped on Tuesday due to the dangerous conditions inside the tunnel, where toxic gases have accumulated and the visibility is very low.

Construction accidents are not uncommon in India. In Himalayan region, fragile mountains, seismic activities and unpredictable underground conditions make tunnel projects very risky.