Guwahati: Ten people were killed while several others remained trapped after an under-construction tunnel collapsed due to a landslide in Sikkim's Namchi district a day ago, officials said on Tuesday.A total of 25 people, including project officials and workers, were trapped inside the tunnel when it collapsed on Monday. "Ten bodies have been recovered so far. Seven of the deceased have been identified, while three unidentified bodies were sent to District Hospital Singtam and STNM Hospital," Namchi Police said in a statement.Also Read: Delhi Court directs compliance with injunction in entrepreneur Ankiti Bose defamation suit, seeks affidavit from defendantNHPC Limited, in a statement on Tuesday, said, "An unfortunate incident occurred at 1:04 pm on July 20 inside the under-construction Head Race Tunnel of NHPC Teesta Stage-VI Hydroelectric Project, Samardung, South Sikkim, after a sudden burst of suspected methane gas trapped within the rocks led to an explosion, generating dense fumes and toxic gases. The project team immediately activated its emergency response protocols. The team is working in close coordination with the district administration, National Disaster Response Force, State Disaster Response Force, local authorities and other emergency agencies to support the ongoing rescue operations. In addition, a special rescue team from DG Mines Safety has also reached the site."The company added, "As per the latest information from the site, 25 personnel were trapped inside the tunnel, of whom 10 have been confirmed dead so far." NHPC said a detailed investigation will be undertaken to ascertain the cause of the incident.Also Read: Meghalaya launches Rs 175.45 crore ‘Mission Golden Spice’Sikkim chief minister Prem Singh Tamang said the tunnel at Samardung in Jholungey caved in due to a landslide.Tamang said Prime Minister Narendra Modi spoke with him and enquired about the rescue operations. "Following the inquiry, if any fault or negligence on the part of the company is found, appropriate action will be taken. The state government will also provide ₹4 lakh as compensation to the families of the deceased and ₹50,000 to the injured. There were 27 people inside the tunnel, of whom two managed to escape," he said.Following the tragic incident at the under-construction tunnel of the NHPC Teesta Stage VI Hydroelectric Project at Samardung, Jholungey, in Namchi District, Hon'ble Prime Minister Shri Narendra Modi Ji spoke with me to enquire about the situation and the ongoing rescue…— Prem Singh Tamang (Golay) (@PSTamangGolay) July 21, 2026 The CM said he is closely monitoring the rescue operation. "Following the tragic incident at the under-construction tunnel of the NHPC Teesta Stage VI Hydroelectric Project at Samardung, Jholungey, in Namchi district, Prime Minister Narendra Modi spoke with me to enquire about the situation and the ongoing rescue operations," Tamang posted on X.