SILKYARA TUNNEL, India — India's infrastructure push into the ecologically fragile Himalayan mountains has been given a "wakeup call" by the collapse of a road tunnel that trapped 41 men, environmental experts said.

The partial cave-in of the under-construction Silkyara road tunnel in northern Uttarakhand state nearly two weeks ago — with the desperate men still awaiting rescue on Friday — was only the latest disaster in the geologically unstable region.

Raghav Chandra, ex-chairman of the National Highways Authority of India, warned that "building a tunnel through a mountain is perilous", but dangers were multiplied when such large-scale projects are poorly carried out.

It came as officials said on Friday that just a few meters of rock and earth separate rescue teams from the workers, adding that they were optimistic of success within hours.

After a series of rapid advances, hopes that the men's freedom was imminent were dashed late on Wednesday when the drilling machine powering through tons of rock and concrete ran into metal rods, but those have now been cleared.

Rescue teams have stretchers fitted with wheels ready to pull the exhausted men through 57 meters of steel pipe — once it has been driven through the final section of rubble blocking their escape.

"We have to (drill) 14 meters further inside the tunnel," Bhaskar Khulbe, a senior government official overseeing rescue efforts, told reporters on Friday.

"If everything goes well, we hope to reach them by today evening," he said, adding that the "trapped workers are in good frame of mind".

But a government statement has noted that any timeline was "subject to change due to technical glitches, the challenging Himalayan terrain, and unforeseen emergencies".

The area outside the 4.5-kilometer tunnel has been a flurry of activity, with worried relatives gathering and rescue teams stopping to pray at a Hindu shrine erected at the entrance.

Ambulances are on standby and a field hospital has been prepared to receive the men who have been trapped since a portion of the under-construction tunnel in the Himalayan state of Uttarakhand caved in 13 days ago.

Agencies Via Xinhua