Mining operations at platinum mines in Rustenburg - in South Africa's North West province - would be gradually ramped up to full production by Monday, said Johan Theron, spokesperson for Impala.

The Johannesburg-based platinum shut down most of its mines in South Africa after an accident at its No. 11 shaft killed 11 workers and saw another 75 hospitalised on Monday. Impala said Wednesday another employee had succumbed to injuries, raising the toll to 12.

"The process to resume production starts today but we will be close to normal production from Monday next week," Theron told Reuters.

Impala is among South African companies that operate some of the world's deepest and ageing platinum mining shafts. South Africa is the world's top supplier of platinum, which is used in devices that help curb toxic vehicle emissions.

The mine where the incident took place would probably restart next year, said Theron, declining to say how the closure would impact group metals output.

The No. 11 shaft accounts for about 15% of Impala's platinum-group metals production at the Rustenburg mining complex.

"It's safe to assume that it will be up early next year but our primary consideration right now is not to count ounces," Theron said.

Bank of America Securities analysts said the affected shaft has an annual output of about 173,000 ounces and could be out of use for as much as 18 months, impacting earnings.

"We take a view and reduce assumed production by this volume for the...remainder of FY2024 (June year-end) and all of FY2025," BofA Securities said in a Nov. 28 note.

(Reporting by Felix Njini; Editing by Stephen Coates and Bernadette Baum)