Four people were shot and wounded by security guards at Gold One’s flagship Modder East mine near Springs early on Monday, police said.
Spokeswoman Captain Pinky Tsinyane said police were called to the scene at 6.30am, but arrived after the men had been taken to hospital.
One of the four was in a critical condition, while the other three had less serious injuries.
Tsinyane said some of the men had previously been fired from the mine, apparently over union recognition issues, but some had since been reinstated.
Police were investigating a case of attempted murder and four people were arrested for public violence.
Independent Online reported that a crowd gathered outside the gates of Modder East on Monday morning, demanding to be re-employed with higher salaries.
Workers, who had been on strike since June 4, were reportedly fired via sms on June 11 for going on strike.
Further details were not available. -Sapa