The bodies of all 25 workers have been retrieved from an under-construction NHPC hydropower project tunnel that had collapsed in Sikkim’s Namchi district, officials said on Thursday.The labourers were inside the NHPC Teesta Stage VI Hydropower Project tunnel under construction, which collapsed following an explosion suspected to have been caused by methane gas shortly after 1 pm on Monday.All the bodies have now been recovered after 72 hours of continuous search operations, KK Roy, a member of the rescue team from Eastern Coalfield Ltd, told reporters.“The Sikkim Government, district administration, and all concerned agencies continue to closely monitor the situation, while extending every possible support to the affected families,” a state government official said.Eight bodies had been identified till Wednesday. Of them, four are from Jalpaiguri district of West Bengal while one each from Punjab, Uttarakhand, Assam and Sikkim.At least four workers from Jharkhand’s Khunti, Hazaribag and West Singhbhum districts were engaged there, another official said.NHPC on Wednesday announced an ex gratia of Rs 5 lakh for the next of kin of each person who died in the accident.Sikkim Chief Minister Prem Singh Tamang on Tuesday announced Rs 4 lakh ex gratia for the next of kin of each of those workers who died in the accident, and Rs 50,000 for every injured person.Prime Minister Narendra Modi also announced an ex gratia of Rs 2 lakh for each of the next of kin of the deceased, and Rs 50,000 each to the injured persons.According to an NHPC statement, a sudden burst of suspected methane gas trapped/embedded inside the rocks led to the explosion, generating dense fumes and toxic gases in the tunnel.