The fire broke out late yesterday some 1.7 kilometres beneath the surface at the firm's Doornkop gold mine.
Eight employees are in the process of being rescued from an underground refuse bay, but nine more are still feared trapped.
"The rescue teams are continuing to try to locate the other individuals who are unaccounted for -- there are still nine employees who are unaccounted for," said spokeswoman Charmane Russell.
"Rescue teams were immediately dispatched underground, but access to the affected area is being hampered by smoke and a subsequent fall of ground," the company said.
Operations at the mine have been suspended.