"Production at the concentrating plant is halted until further notice [but] mining production is unaffected," the company said.

Kevitsa produced 27,498 tonnes of copper in concentrates, 13,948 of nickel in concentrates and 591 tonnes of cobalt in those nickel concentrates during the 2018 calendar year, it reported.

"Clearly if the asset’s primary crusher is down for an extended period, ore can be stockpiled ahead of the plant but this would have a negative working capital impact," RBC analyst James Bell said in a note reacting to the news today.

Fastmarkets' copper concentrates TC index, cif Asia Pacific rose on Friday May 22 to $51.6 per tonne/$5.16 per lb, ending a two-month slide while mines across South America resumed production after coronavirus-related lockdowns.