Stillwater mine have been suspended as officials work to rescue miners stuck underground following a collapse.
"We've got the rescue teams underground and there's a lot of loose rock, so you can imagine the difficulties," mine spokesperson James Wellsted told News24.
He said that 10 of the initial 13 workers who were trapped by what he described as a "seismic event" were freed, but contact had only been made with one of the missing three.
Four miners were confirmed dead.
Association of Mineworkers and Construction Union (AMCU) president Joseph Mathunjwa lambasted the mine over accident, saying that workers were sent down the mine after an earlier seismic event.
"Indeed, this is a sad day. These mines continue killing workers," said Mathunjwa.
Wellsted acknowledged that seismic events were not unusual and argued that the priority for the mine was to rescue the remaining workers.
"We're not trying to get into the battle of one-upmanship with the unions. They are stakeholders and are critical to our business.
"There are other agendas at the moment - there are other issues driving the politics at the moment."
He said that in previous seismic events, there were no rock falls or earth moments and added that a full investigation would be conducted.
"Our safety systems generally work, and we'll have to do the investigations once we get our workers out."