Codelco’s El Teniente Division reported a seismic event that measured 3.9 on the Richter scale, which took place at the ventilation sublevel of the North Andes project at 04:24 hours on Monday, July 24. The El Teniente mine, in central Chile, is the world’s largest underground copper mine.

The event, which was attributed to tectonic movements, triggered a rock burst inside the new Andes Norte mine level. A contractor, who had been trapped by a cave-in, was successfully rescued without significant injuries. The miner was “in good condition and always in communication,” according to Codelco. A dozen workers were also safely evacuated from the area.

El Teniente has been in operation since 1905. It is a block-caving operation and last year it produced more than 405,000 metric tons of copper.