A jagged rocky hole just big enough for a man to pass through is all the Nova Scotia Minehunters need to enter the abandoned Crows Nest gold mine in Guysborough County, about 250 kilometres east of Halifax.

The tunnel is cramped and dark. Sections of the old mine are submerged in water. In some areas there are vertical shafts dropping 60 metres or more.

There's rotted wood and areas of the mine appear to have caved in, but none of that deters the small group of explorers. They slowly continue their descent — pursuing a hobby they've carried out in about 20 mines across Nova Scotia.

The hunters explore mines for the thrill of discovery. But Nova Scotia's Department of Natural Resources and a miners union said the group is playing a deadly game that needs to stop immediately.

In some cases, the mine hunters believe they are among the first to journey into these neglected sites in decades or even more than a century.

The Nova Scotia Minehunters digitally alter their faces and voices in pictures and videos to hide their identities. In this image, the group is in the abandoned Crows Nest gold mine. (Nova Scotia Minehunters/Facebook)

Their videotaped exploits have earned thousands of views on YouTube, but the mine hunters are careful to keep their identities secret by altering their voices and hiding their faces.

Many of the mines the men visit are on private property, and in most cases they don't ask for permission to enter.

When contacted by CBC News, the group said anonymity helps its members avoid anyone who may want to stop their exploration. It also helps them avoid being prosecuted for trespassing.

More than 1 way to be killed

Bob Burchell of the United Mine Workers of America says exploring abandoned mines isn't a game. (Nic Meloney/CBC)

There are hundreds of ways an old mine could turn deadly for the hunters, said Bob Burchell of the United Mine Workers of America. Cave-ins, falls, contaminated mine water and poisonous gas are just a few.

"This is not thrill-seeking. This is something that will kill you," he said.

The mine hunters equip themselves with hard hats, head lamps, and other gear before they head into a mine. (Nova Scotia Minehunters/Facebook)

"There's countless dangers working in an operating mine, let alone going in one that's been abandoned for years and not having any experience and not knowing what you're doing.

"It's a ticket for disaster."

A handbook from the Department of Natural Resources explains that mine openings were not built to last forever. The entryways can become unstable as supports start to deteriorate and rocks weaken and fracture.

'Why would you want to do that?'

Ernie Hennick, a mine-planning technician with the department, said he was shocked by the mine hunters' videos.

"I couldn't believe what I was watching," he said. "Some of what these guys are doing underground [is] incredibly risky. Why would you want to do that?"

The Nova Scotia Minehunters have explored and filmed about 20 abandoned mines in the province. (Nova Scotia Minehunters/Facebook)

Both Burchell and Hennick said the mine hunters are putting themselves and others at risk. If anything should happen during an exploration, rescue workers would be put in danger trying to save them.

The group said the risks its members take are no different from rock climbers or people who explore caves. The men in the videos wear protective gear, including hard hats, and use ropes and head lamps.

Members say they try not to disturb anything while inside a mine and they generally only enter hard rock mines that are less likely to have deadly gases like methane trapped inside.

Thousands of deserted mines in N.S.

The mine hunters said they do extensive research before they enter a mine, often using public files from the Department of Natural Resources to locate deserted mines and find maps of their interiors.

The department said there are about 8,000 abandoned mines in Nova Scotia, many in the backwoods off the beaten path. About 25 per cent of them are on Crown land.

The mines the group visits have been left opened, but do have signs warning people of the dangers of going inside. (Nova Scotia Minehunters/Facebook)

The province has blocked the openings to several of those mines and is working on sealing others.

Private landowners are required to post signage warning people of the openings and try to guard an open hole to prevent people from being injured.

'They don't realize the danger'

In their videos, the mine hunters warn people not to go into abandoned mines and instead to live vicariously through them as they explore.

Burchell said the hunters should take their own advice.

"They think it's an adventure," he said.

"They don't realize the danger that's there."