An equipment failure at a former Colorado gold mine has left one person dead and a dozen others trapped, authorities said Thursday.

The elevator descending into the Mollie Kathleen Gold Mine, which now operates as a tourist site, near the town of Cripple Creek, had a mechanical issue around 500ft (152 meters) beneath the surface. It created a “severe danger for the participants” and one person was killed, Jason Mikesell, the Teller county sheriff, said at a press conference.

Crews were able to rescue 11 people, but 12 people are still at the bottom of the mine, about 1,000ft (305 meters) deep. They are in safe conditions and in communication with authorities, said Mikesell. Rescuers are working to get the elevator back online.

The sheriff said they could rescue the trapped group by rope if necessary, but were hoping to get the elevator system working.

Mikesell said the last time there was an incident was 1986.

The mine opened in the 1800s and was closed in the 1960s but still operates tours. The mine’s website describes a one-hour tour in which visitors descend 100 stories into the earth. It says visitors can see veins of gold in the rock and ride an underground tram.

The Colorado governor, Jared Polis, said in a statement that the state was sending resources for the rescue effort.

“We will do everything possible and assist the county to ensure a speedy and safe resolution of the situation,” said Polis.