The company said an electrical technician was injured while working on an underground voltage regulator. It said he was immediately transported to hospital, where he later passed away.
Capstone said it was committed to the highest safety standards at its operations and sincerely regretted those efforts did not prevent the incident.
"Our heartfelt sympathy goes out to our miner's family and our entire team at Cozamin," president and CEO Darren Pylot said.
Capstone said operations had resumed, except in the immediate area of the accident, which was secured for an ongoing investigation.
The company also operates the Pinto copper mine in the US and the Minto copper mine in Canada, which it recently agreed to sell to Pembridge Resources (LN:PERE).