At least 20 workers were killed and five others remained trapped for over 24 hours after a tunnel under construction collapsed in Sikkim's Namchi district following an explosion of suspected methane gas, a police officer said on Tuesday. Chief Minister Prem Singh Tamang announced Rs 4 lakh as ex-gratia for the next of kin of each of those workers who died in the collapse of the NHPC tunnel and Rs 50,000 for every injured person. Prime Minister Narendra Modi spoke to the chief minister and took stock of the situation, besides assuring him of all help from the central government. The PM also announced an ex-gratia of Rs 2 lakh to the next of kin of the deceased and Rs 50,000 each to the injured persons. As many as 25 workers, including a few project officers, had been trapped inside the collapsed tunnel of the NHPC Teesta Stage VI Hydropower Project at Samardung shortly after 1 pm on Monday