Officials were investigating Sunday what caused a crack in a Colorado ski lift that forced the evacuation of over 170 stranded skiers and snowboarders.

The gondola lift at Winter Park Resort, about 70 miles (113 kilometers) west of Denver, automatically stopped when it detected the crack in a structural piece of the lift just after noon on Saturday, resort spokesperson Jen Miller said. People riding in the gondolas were lowered down by ropes over the course of about five hours, she said.

No injuries were reported during the rescues, which came at the start of the busy holiday ski season.

Ski patrolers entered the cabin of each gondola from above and lowered people’s equipment to the ground before using a rope equipped with a seat to lower each of the 174 passengers to the ground, Miller said.

Workers were replacing the section of the lift that cracked Sunday as state regulators and the lift’s manufacturer worked with resort officials to investigate what caused the crack, Miller said. The resort still had 21 other lifts open.

(AP)