Drilling with a new machine started on Thursday and has covered a stretch of 24 metres, Devendra Patwal, a disaster management official, said.
It might require up to 60m to enable the trapped workers' escape, Patwal told the Associated Press.
Patwal said the rescuers hoped to complete the drilling by Friday night and create an escape tunnel of pipes welded together.
Some of the workers felt fever and body aches Wednesday, but there has been no deterioration in their condition, he said.
Nuts, roasted chickpeas, popcorn and medicine are being sent to them via a pipe every two hours.
The construction workers have been trapped since Sunday, when a landslide caused a portion of the 4.5km tunnel they were building to collapse about 200m from the entrance.
The hilly area is prone to landslide and subsidence.
The site is in Uttarakhand, a mountainous state dotted with Hindu temples that attract many pilgrims and tourists.
Highway and building construction has been constant to accommodate the influx.
The tunnel is part of the busy Chardham all-weather road, a flagship federal project connecting various Hindu pilgrimage sites.
About 200 disaster relief personnel have been at the site using drilling equipment and excavators in the rescue operation, with the plan to push 80-centimetre-wide steel pipes through an opening of excavated debris.
A machine used earlier in the week was slow in pushing the pipes through the debris, a state government statement said.
The new American Auger machine has a drilling capacity of up to 5m per hour and is equipped with a 9.9m diameter pipe to clear debris.
