Teller County, Colorado - One person died, and a dozen people remain trapped deep in a disused Colorado gold mine after the shaft's elevator system malfunctioned during a tour Thursday, local police said.

The incident occurred during the Mollie Kathleen Gold Mine Tour, which takes visitors 1,000 feet underground in the western state.

A group of visitors were on board the elevator trolley system when the mechanical failure occurred, killing one person and injuring four.

Officials did not release further details about what went wrong, citing an active investigation.

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"We did have one fatality that occurred during this issue at 500 feet," Teller County sheriff Jason Mikesell told a press conference.

The other 11 people on board the elevator at the time, including two children, were brought safely to the surface with the assistance of the mine operators and fire department officials.

Aside from the fatality, the four people hurt in the incident suffered only minor injuries, said Mikesell.

A further 12 people remain in a tunnel at the bottom of the mine.

They are safe and are accompanied by a mine employee, but cannot be moved until the elevator system is cleared as safe to be used again, said Mikesell.

Emergency officials with ropes are standing by in case they are required. Chairs, blankets, and water have been provided to those in the mine.

"The atmospherics are good inside the tunnel," said Mikesell.

Those still inside the mine have not been informed of the fatality.

"We're just trying to keep down the worry of what's going on, so that nobody gets excited," added Mikesell.

The mine outside the small city of Cripple Creek, around 100 miles south of Denver, offers a chance to "Experience the 'Old West' as it was for hard rock gold miners of 'The World’s Greatest Gold Camp,'" according to its official website.