Twelve people were rescued Thursday evening after being trapped for six hours at the bottom of a former gold mine in Colorado when an elevator failed, killing one person, authorities said.

The incident occurred at the Mollie Kathleen Gold Mine, a tourist spot near Cripple Creek.

According to Teller County Sheriff Jason Mikesell, the elevator was descending into the mine when a mechanical problem occurred about 500 feet below the surface.

The accident posed what Mikesell called a “serious danger to participants” and resulted in the death of one person. The sheriff declined to release the identity of the deceased person.

The twelve adults were trapped about 300 meters underground. Despite the dire situation, they had access to water and the underground atmosphere was considered safe. While they waited to be rescued, they were in contact with authorities via radio.

Mikesell said the group remained in good spirits and, after being brought to safety, were given pizza and given full details of the incident. While they were trapped, all they were told was that there was a problem with the elevator.

The cause of the elevator malfunction remains unknown and an investigation is ongoing. Engineers worked to ensure the elevator was operating safely before using it to transport the group back to the surface.

Rescuers were prepared to use ropes if the elevator repair was unsuccessful. The incident, first reported around midday, occurred in the final week of the mine’s tourist season before its winter closure.

Newsweek Gold Mine emailed Mollie Kathleen for comment.

Earlier in the day, another group of 11 people had been rescued from the same elevator. Four of them suffered minor injuries, but Sheriff Mikesell did not say how they were injured.

According to the mine’s website, the elevator typically takes two minutes to descend and moves at a speed of about 500 feet per minute.

The last known incident at the mine occurred in the 1980s, when some people became trapped in the elevator, but no fatalities were reported.

Mines that serve as tourist attractions in Colorado are required by the state to have a designated person inspect the mines and transportation systems daily, according to the Department of Reclamation, Mining and Safety. Sheriff Mikesell did not know when the last inspection took place and online inspection records were not immediately available.

Colorado Governor Jared Polis dispatched state resources to help with the rescue, including a mine rescue team. Cripple Creek, a small town of about 1,100 residents, is located in the Rocky Mountains, southwest of Colorado Springs.

The Mollie Kathleen Gold Mine opened in the late 19th century and operated until 1961, but continues to offer tours for visitors.

The mine’s website has a description of the tour, which includes a 1,000-foot descent and the opportunity to view gold veins in the rock. The site is named after Mollie Kathleen Gortner, who discovered the mine in 1891.

This article contains reporting from The Associated Press