Rescue teams continued their efforts on Wednesday to trace the individuals, including Kerala geologist Anish Mohan, who remain missing inside the collapsed tunnel of the NHPC Teesta Stage-IV hydroelectric project in South Sikkim following an explosion.

Meanwhile, the bodies of three consultants who had entered the under-construction tunnel along with Anish were recovered and identified on Wednesday, Anish’s brother Binish told Onmanorama. He said waterlogging inside the tunnel following the landslide has severely hampered rescue operations.

Anish Mohan, 43, is a Senior Geologist (Remote Sensing) with NHPC and a native of Illivalavu in Manarcad, Kottayam. He has been working with NHPC since 2011.

According to Binish, Anish was not originally scheduled to enter the tunnel. He was asked to accompany a four-member team of NTPC consultants and civil engineers who wanted to inspect the site on Monday, when the collapse occurred. “We were told that a team of four, consultants and engineers, wanted to visit the tunnel, and Anish was asked to take them inside,” Binish said.

According to national media reports, at least 20 people have died in the incident. “However, it is yet to be confirmed how many ordinary workers engaged in the tunnel project remain trapped in the debris,” Binish added.

Binish said two photographs received from the authorities at the site helped rescue officers identify the five-member team, including Anish, who had entered the tunnel before the accident. In one photograph, Anish was seen with the consultants and engineers during their tunnel inspection, while another showed him in a discussion with the team hours before they entered the site.

“The exact time of the first photograph is not known, but the other picture was reportedly taken only hours before they entered the tunnel. These images helped officials identify those who were missing,” Binish said.

A team of the National Disaster Response Force (NDRF) joined the rescue operation on Wednesday, while assistance from the Air Force has also been sought, Binish said.

Meanwhile, NHPC announced a compensation of ₹5 lakh to the next of kin of each person who died in the incident. In a statement, the company said rescue operations at the Head Race Tunnel (HRT) of the Teesta Stage-IV hydroelectric project were continuing round the clock with the coordination of the district administration, NDRF, SDRF, NHPC, Patel Engineering, Eastern Coalfields, Western Coalfields, local authorities and other agencies.

According to NHPC Limited, the incident occurred around 1.04 pm on July 20 inside the under-construction Head Race Tunnel at Samardung in South Sikkim. A sudden release of suspected methane gas trapped inside the rocks is believed to have triggered an explosion, causing dense fumes and toxic gases inside the tunnel.

Binish, who works as an engineer in Dubai, reached the accident site soon after learning about the incident. He said rescue teams have identified the possible location of the trapped, but toxic gases and accumulated water have made access difficult.

“The rescue operation is highly complicated. They are trying all possible methods, including pumping out water. Toxic gas has filled the tunnel, and the oxygen supply line has also been damaged,” Binish said.

Anish and his wife Sangeetha had recently moved from Haryana to Sikkim following his transfer. Sangeetha later returned to Tripunithra, Kerala, for the birth of their second child. Anish had visited his wife and newborn earlier this year in February. His parents, Mohanan and Amminikutty, live at Illivalavu in Kottayam.