Rescuers attempting to free 41 workers trapped inside a collapsed tunnel in India were forced to dig by hand on Saturday after their drilling machine failed.

Part of the Silkyara tunnel in the mountainous Indian state of Uttarakhand collapsed on November 12.

Rescuers were attempting to drill horizontally through 57 meters (187 feet) of rock and concrete when their machine ran into metal rods and construction vehicles that were buried in the earth.

This caused the drilling machine, known as an auger, to become damaged just nine meters away from the trapped workers.

"The machine is busted. It is irreparable," Arnold Dix, an international expert assisting with the rescue, told reporters at the site.

"The mountain has once again resisted the auger."

'We will proceed manually'

Government officials said workers would attempt to cut through the final nine meters using hand-held power tools.

"We will proceed manually," Uttarakhand Chief Minister Pushkar Singh Dhami told reporters.

Syed Ata Hasnain, a member of the National Disaster Management Authority which is overseeing rescue efforts, said the operation was becoming "more complex" and the process would become slower, compared to when the auger was used to drill.

"We have to strengthen our brothers stuck inside. We need to monitor their psychological state, because this operation can go on for a very long time," he added.

Second machine brought in to dig vertically

Rescuers have also hatched an alternative plan to reach the survivors from above.

A new machine was brought in on Saturday and taken to the top of the hill via a specially-created track.

However, this dig would be almost double the length of the horizontal dig and is a risky route in an area that has already suffered a collapse.

Workers 'in good spirits'

The workers trapped inside the tunnel have been supplied hot meals of rice and lentils through a 15-centimeter pipe.

Oxygen is being supplied through a separate pipe, and a team of doctors including psychiatrists are monitoring their health from outside the tunnel.

"They are in good spirits," said Rharm, the Uttarakhand chief minister.

"They said: 'Take as many days as you require, don't worry about us.'"

Many of the trapped workers are laborers from other parts of the country.

Their families have traveled to the accident site and camped outside for days to receive updates about their wellbeing.

zc/dj (AP, AFP, Reuters)