At least 11 people died at a mine owned by Impala Platinum Holdings Ltd. when an elevator transporting workers to the surface failed, the worst accident in the South African company’s history.

The incident occurred Monday afternoon, when the so-called personnel conveyance that was hoisting employees “unexpectedly started descending,” the company said in a statement Tuesday. Its descent was stopped by a counterweight becoming trapped, it said. Another 75 workers were injured in the accident and have been hospitalized.

“This is the darkest day in the history of Implats,” Chief Executive Officer Nico Muller said in the statement. Operations are suspended and an investigation is being conducted into the cause of the accident.

South Africa’s mining industry has been struggling to reduce such fatalities. The 18% increase in deaths to 52 from 44 by the same time last year makes this year the worst for the industry since 2021, according to data provided by Implats and Minerals Council South Africa, an industry lobby group.

Implats’ shares fell as much as 7.7% and traded 7.4% lower at 77.60 rand by 11:55 a.m. in Johannesburg.

After the accident at Implats’ 11 Shaft in the northern city of Rustenburg, all available ambulances from other mining operations were sent to the mine to transport injured employees to nearby hospitals, Japie Fullard, chair of the Minerals Council’s CEO Zero Harm Forum, said in a separate statement.

The company’s Rustenburg operations account for about a third of production. Impala gained control of Royal Bafokeng Platinum Ltd. in May to extend the life of the complex, from which the company has been producing platinum for more than five decades.

--With assistance from William Clowes.

(Updates throughout with details of accident, shares and mining safety)