Three miners are trapped and one has died after a rockfall at an AngloGold Ashanti mine near Carltonville.
AngloGold Ashanti spokesperson Chris Nthite said a seismic event at the Mponeng Mine near Carltonville, on Johannesburg's West Rand, had caused the collapse.
Nthite said rescue operations had been underway since the collapse, and that four miners had been rescued.
Three miners were still trapped and one had died, he said.
Nthite said the conditions of the three trapped miners was unclear, but they would work until they had been rescued.
"We are working under challenging conditions and we will be working around the clock to get to the other miners."
The National Union of Mineworkers (NUM) said it was "disturbed and saddened" by the incident.
NUM health and Safety secretary Erick Gcilitshana said: "This fall of ground was triggered by a seismic event of 1.1 magnitudes that took place at around 10:00 this morning. This is the third incident since last month.
"The search team is able to communicate with one worker. The rescue operation has started. The NUM wishes all six workers to be rescued alive," he said.