Dozens of workers trapped in a Canadian mine are in the process of making a dramatic escape that involves climbing vertically for up to 10 hours.

Thirty-nine employees at the Totten mine in northern Ontario were trapped underground starting midday on Sunday when its elevator system was damaged, according to Brazilian mining company Vale.

The workers stayed in underground “refuge stations” with a significant supply of water and received deliveries of food and medication from rescue teams, according to the United Steelworkers union, whose Local 6500 chapter represents 30 of the 39 miners.

The climb to safety

Rescue crews started moving them out on Monday using a process that involves a long climb up a series of steep ladders.

The exhausted miners, who had been in the mineshaft for more than a day when the rescue mission started, are wearing harnesses as they make the 0.6-mile ascent, according to the BBC.

The miners were coming from the depths of between 900 and 1,200 meters (or roughly 2,952 to 3,937 feet). The Toronto Star notes that the city’s famous CN Tower “pales by comparison at 553 metres spread out over 1,776 steps.”

Shawn Rideout, the chief mine rescue officer at Ontario Mine Rescue, said the climb could take up to 10 hours to complete and that there are rest stops every 100 meters (or about 330 feet) if workers need a break.

Citing Ontario Mine Rescue, the CBC reports that some workers unable to complete the climb may be “hoisted out using ropes.”

Happy to see the sunshine

At least 33 miners had reached the surface as of mid-Tuesday morning, per the CBC.

USW District 6 said Tuesday morning that a team of doctors is checking the miners as they emerge, and that no one has been injured in the incident or evacuation process. Miners are being given rides home, it added.

“When an incident like this unfortunately happens, everyone comes together,” said Nick Larochelle, USW Local 6500 president. “The miners support each other, the highly trained mine rescue teams come together and the whole community waits patiently praying for the safe return of every one of the 39 miners to surface.”

Rideout originally said rescuers expected to get the rest of the miners out by 11 a.m. ET, but noted that “they’ve been underground for more than 48 hours, so we are taking it slow.”

He told the CBC that the miners who have made it out so far are in good spirits.

“Everybody’s doing fine here,” he said. “The workers come up, they are obviously happy to see the sunshine. But it’s smiles all around and everything’s progressing very well.”

Reporting for this story originally appeared in the Morning Edition live blog.