One of the two men who were trapped in a mine on Stanley Road in Primrose, Germiston, has died, paramedics said on Thursday.
He was brought to the surface around 18:00 and declared dead on the scene, ER24 spokesperson Annine Siddall said. He had run out of oxygen.
The owner and one employee of the mine had descended more than 75m into the mine to check on water levels around 15:00.
"Fire and rescue workers have had great difficulty in bringing both men to safety and will now bring the second man to the surface of the mine as soon as possible," Siddall said.
Local authorities were investigating.