Rescuers drilled about one-third of the way into the debris of a collapsed highway tunnel in Uttarakhand by Friday morning to reach 40 workers trapped inside for five days, officials said.
Drilling had penetrated through about 21 metres (70 feet) of debris, Devendra Singh Patwal, said a disaster management officer.
They have to cover a total distance of nearly 60 meters.
Another officer with the rescue team inside the tunnel said the trapped men were doing fine.The workers have been supplied with food, water and oxygen through a pipe and authorities have been in contact with them via walkie-talkies.
The 4.5 km (3 mile) tunnel in the northern state of Uttarakhand is part of the Char Dham highway, one of the most ambitious projects of Prime Minister Narendra Modi's government.
Authorities have not said what caused the tunnel to cave in on Sunday morning, but the region is prone to landslides, earthquakes and floods.