Two Harmony Gold employees were killed in a "fall of ground" incident at the Kusasalethu mine, near Carletonville, in Gauteng.
The mineworkers were killed in the early hours of Thursday morning, following a seismic event, and it resulted in the fall.
"The board, executives and management of Harmony are deeply saddened by this tragic incident," said Peter Steenkamp, the CEO of Harmony.
"We extend our thoughts and prayers to the families, friends and colleagues of our deceased colleagues," he added.
The gold mine company said the relevant authorities and stakeholders had been informed.
"While mining activity in the affected area has been stopped, safety shifts have also been enforced across the mine, pending a formal investigation," Steenkamp said.