DENVER >> Investigators on Friday were trying to figure out what led to an elevator accident inside a former Colorado gold mine that killed a tour guide, injured four others and left a separate group of 12 people trapped for hours at the bottom of the tourist attraction 1,000 feet beneath the surface.

The elevator was descending into the Mollie Kathleen Gold Mine on Thursday in the mountains near Colorado Springs. At around 500 feet down, the person operating the elevator from the surface “felt something strange” and stopped it, Teller County Sheriff Jason Mikesell said.

The elevator was still operable, and those on board were brought back up within 20 minutes, the sheriff said. A door on the elevator was broken when it was raised.

“We don’t know if the door malfunctioned or not or if something else occurred. There’s a lot that goes on in these little elevators,” he said. “We just know that the door was broken somehow.”

The man killed, Patrick Weier, 46, had a young child and was from the nearby town of Victor, Colorado. The exact circumstances of his death were not disclosed, but the sheriff said he died because of the elevator’s mechanical issue and not due to a medical issue.

Eleven other people, including two children, who were riding the elevator during the mishap were brought up with it following the accident. Four had minor injuries including back pain, neck pain and arm pain, the sheriff said.

Twelve adults from a second group were trapped below ground for about six hours while engineers made sure the elevator could be used. The group had access to water and used radios to communicate with authorities, who told them there was an elevator issue, Mikesell said.

They were hoisted up in groups of four over 30 minutes. Officials had been prepared to bring them up by rope if necessary. Most people who were in the elevator when it malfunctioned were later taken to a local relief center, where some got showers, new clothes and sandwiches, said Ted Borden with the Community of Caring Foundation in Cripple Creek.

“It was still very raw, but there was some good camaraderie,” Borden said.

Elevator accidents at mines are extremely rare, said Steven Schafrik, a University of Kentucky associate professor of mining engineering. They have been used by the industry to carry people and material since the mid-1800s, he said, and modern elevators are equipped with fail-safe devices that prevent them from falling far if a cable breaks.“They’re just ridiculously safe,” Schafrik said of mining elevators. He declined to comment directly on the Colorado accident.

Mikesell said the family that owns the mine had run it as a tourist attraction for generations and worked to make it safe. Mines that operate as tourist attractions in Colorado must designate someone to inspect the mines and the transportation systems daily, according to the state Division of Reclamation, Mining and Safety.