Two miners died when a rock fell on their heads while drilling in shaft 12 of Impala Platinum's Rustenburg mine on Tuesday morning, the mine said.
The two men, aged 31 and 34, died at the scene, Impala Platinum spokesperson Johan Theron told News24.
He said the rock fall did not threaten the lives of any other miners.
"We are presently launching a full investigation into the circumstances of the incident. The safety of our employees enjoys priority."
Theron said the mining group is assisting the family of the deceased miners as far as possible.
Mineral Resources minister Mosebenzi Zwane said the ministry will be conducting an investigation into the cause of the accident.
"We are extremely concerned ... with these incidents which continue to claim the lives of workers in the mines. We have a duty and legislative obligation to investigate these incidents with a view to ensuring that as far as possible we prevent them," Zwane said in a statement.