The company's Huanzala and Palka mines, which were closed on March 16 due to a government lockdown, restarted operations on July 2 after the company put safety measures in place and secured local government approval.

"The mines' operations have returned to the levels before the quarantine was put in place as they have been preparing for the restart since late June," a company spokesman told Reuters.

Huanzala is a lead-zinc mine with a 1,200t/d capacity that has has been operating for 52 years. It is operated by Cia Minera Santa Luisa and owned by Mitsui.

Palka, which started large-scale production in 2006, produces zinc, lead and silver.