Rescuers trying to reach workers trapped for nearly a week in a collapsed highway tunnel in the Indian Himalayas are working to replace the main digging machine on Saturday to restart operations after they hit a snag.

The disaster management office revised the number of people trapped since Sunday morning in the tunnel in Uttarakhand state to 41, up from 40. All are safe, the authorities have said.

The augur machine drilling through the debris broke on Friday.

A new machine flown in from the central Indian state of Madhya Pradesh, has reached the site, Anshu Malik Halko, director at state-run National Highways and Infrastructure Development Corporation (NHIDC) told Reuters.

“We will first bring out the defunct machine from inside and then deploy the new one. This will take time and I cannot comment on the timeline. It’s a delicate and risky operation,” Halko said.

Authorities have not said what caused the 4.5-km tunnel to cave in, but the region is prone to landslides, earthquakes and floods.

Fifty to sixty workers were on the overnight shift at the time of the collapse, and those near the exit got out of the tunnel on the national highway that is part of the Char Dham Hindu pilgrimage route.

Work was suspended on Friday after a “large-scale cracking sound” was heard as rescue workers sought to restart the drilling machine, according to a report from NHIDC.

Close to 100 tunnel workers gathered at the site on Saturday, demanding faster progress in reaching and freeing those trapped.

Vishnu Sahu, a labourer who was leading the protest, said the rescue team is keeping workers in the dark about the pace of progress of the rescue.

“We want the top people of the company to come here,” Sahu said.