As rescuers race to save the men, India has sought advice from the Thai company that rescued children from a flooded cave in 2018, as well as engineering experts in soil and rock mechanics at the Norwegian Geotechnical Institute.
Rescuers have been communicating with the trapped men using radios.
Food, water, oxygen and medicine have also been sent to the trapped workers via 15cm wide pipe.
No official details have been given about the condition of the men, but local media reported that some were suffering from vomiting, headaches, anxiety and stomach problems.
A six-bed field hospital has also been set up outside the site with ambulances on standby to transfer serious cases to a proper hospital.
The 4.5km tunnel was being constructed between the towns of Silkyara and Dandalgaon to connect Uttarkashi and Yamunotri, two of the holiest Hindu shrines.