The producer said that, with an improving silver market, it will be ramping up to a throughput target rate of 1,200 tonnes per day. It will be evaluating its studies in the second half of the year as well the nexts steps for Cusi.

Cusi's care and maintenance had been government-mandated as Mexico worked to contain the spread of COVID-19. The idle period, Sierra management said, offered it an opportunity to "complete an optimised review of the entire operation" including future development.

"Management expects that silver will become a significant contributor to the company's revenue mix with the restart of the Cusi silver mine when combined with the silver by-product credits from the company's Yauricocha and Bolivar mines and the recent marked improvement in the silver metal price," CEO Luis Marchese said.

In 2019, Sierra Metals produced a total consolidated output of 3.4Moz from its three mines. The Yauricocha polymetallic operation in Peru was the largest contributor with 1.8Moz, followed by Cusi with 936,000oz and Bolivar in Mexico with 640,000oz.

Sierra, which did not outline how many miners were returning to work for the restart, said that it has implemented illness mitigation processes at Cusi.

Copper is Sierra Metals' biggest share of sales revenues, followed by precious metals, then zinc and lead.