KCM predicted that part of the Nchanga Open Pit in Chingola in Zambia’s Copperbelt area will cave in “anytime” in the next five days after geo-technical assessments detected some slope instability.

The slough – or caving in of the ground – manifested so far through tension cracks opening up is likely to stretch approximately 350 metres (0.2 mile) and the estimated volume of the area involved is 8 million cubic metres, CEO Christopher Sheppard said in a statement.

Production was continuing elsewhere except for the at-risk areas which have been shut, a KCM spokesman said.

KCM has implemented measures to protect communities around the mining area and employees from the impact of the slough, Sheppard said.

“I must state in no uncertain terms that our priority is to ensure the safety of people first, and also make sure that KCM, public and private property are safe-guarded.”

The mine has marked out a 90-metre wide hazard exclusion zone in which the potential collapse is expected to occur. It is “at least” 60 metres away from nearby communities, he said.

Apart from the Nchanga open pit, KCM also operates the Nchanga and Konkola underground mines, concentrators, a smelter, a tailings leach plant, and a refinery.