About 1,800 workers are trapped underground at Sibanye Gold Platinum after an incident in the shaft, the company said.
The company may use an adjacent shaft to hoist the workers to the
surface, although there is currently no estimate for when
happen, and spokesman said.
Some rails were transported underground by the shaft and they blocked it, said spokesman James Wellsted.
Sibanye is assessing the shaft infrastructure, which may take a couple of hours, he said.
There were no injuries as a result of the accident.
The workers entered the mine this morning and the incident happened around lunch time, around when they were normally ending their shift, he said.
The incident may revive concerns about safety at Sibanye, which last year experienced and spike in fatal accidents.
About 1,000 workers were also trapped underground for more than a day at one of its gold mines in February 2018 after a power failure.
Sibanye fell as much as 4.1% and 2.7% lower by 16:31 in Johannesburg.
* This story will be updated as and when information becomes available