Corporacion Nacional del Cobre (Codelco) has lost “substantial” output after a strike at its Radomiro Tomic open-pit mine, according to officials who declared force majeure; early this week, however, orders were still being received by customers. Miners walked out over the recent death of a miner—and the lack of disciplinary action against his supervisors. The mine’s general manager resigned, but will remain with Codelco, said CEO Thomas Keller; no one else has been dismissed.

The mine in northern Chile produced one-fourth of the company’s output last year—more than any other mine—accounting for 428,000 metric tons (mt) of copper in 2012. Codelco has now declared force majeure and “the production we are losing is substantial,” Keller said.

Keller said the strike was “illegal” and “totally unjustified.” But “at this point, we still have no problem with our delivery schedule over the medium term.”