Five miners were killed at Gold Fields' Driefontein mine in Carletonville on the West Rand, the mine said on Sunday.
"Gold Fields Limited regrets to report that five employees have lost their lives at the 4 Shaft (Ya-Rona) KDC West mine, near Merafong... when a fire broke out [on Saturday] night," spokeswoman Sharda Naidoo said in a statement.
Fourteen other workers were admitted to hospital for routine observation and were in a stable condition on Sunday morning.
"The entire KDC mine has been closed until further notice."
Mine management "deeply regrets" the accident and an investigation was underway.
The mine said three of the 14 workers had been discharged from hospital and 11 others were in stable conditions.
Executive vice president Peter Turner, said shaft 4 (Ya Rona) had 655 fatality free working days before this incident.
"This incident is highly regrettable in view of the significant safety improvements we've experienced on this mine. This shaft, together with the remaining 12 shafts on the KDC operation, has been closed and we will be co-operating fully with all stakeholders to investigate the cause of the accident," said Turner.
Earlier, spokesman for the National Union of Mineworkers (Num) Lesiba Seshoka said the five died from smoke inhalation while working overtime doing mudloading. Early indications were there was no compressed air in the section where they were working, he said.
Num general secretary Frans Baleni said: "We strongly condemn the company for sending workers on overtime night shift when there is no ventilation."
Num called on the department of mineral resources to investigate the alleged safety lapses.
