The workers are reported to have been 200m into the tunnel in the Himalayan state of Uttarakhand when it collapsed because of a landslide.
Contact has been established with the group and they are being provided oxygen and food, but rescuers have to dig through several metres of debris to reach the men. The rescue operation is being led by the National Disaster Relief Force (NDRF).
NDRF assistant commandant Karamveer Singh Bhandari has told local media that all the workers were safe.
The wet debris was a creating a challenge, he said, but the rescue team was “leaving no stone unturned”.
The Indian Express reports that excavation with shotcreting is under way for 40m of the collapsed tunnel and chimney formation along the tunnel has started. A cavity has been formed 10m above the crown on both sides.
