Operations were shut for the night of Sept. 11 and an estimated 100 employees and contractors were safely evacuated from Kennecott Utah Copper's Bingham Canyon Mine after movement was detected in the area of April's massive landslide, the Dessert News reported.

About 400 ft of material moved a couple hundred feet around 6 p.m., Kennecott spokesman Kyle Bennett said. An excavator operator spotted the shift and raised the alarm, while monitoring equipment registered the activity.

The evacuation is a precaution, and no one was injured, Bennett said.

Employees who operate machinery in the mine receive specific training to watch out for material movement, providing an additional level of security on top of real-time monitoring from mine systems, he said.

"Part of our safety monitoring effort is to train those people to notice visual changes in their surroundings," Bennett said. "This particular employee did notice those changes, and because they noticed those changes, we stopped work immediately and evacuated people from the slide zone."

Earlier this year, a huge landslide buried the open-pit mine under 165 million tons of earth. The most recent material movement was spotted near the top of the previous slide area.