The fall was "seismically induced" and occurred at 2.21am in the 7 Shaft of the mine, near Westonaria, Gold Fields said in a statement.

The seismic event measured 1.5 on the Richter Scale, it said.

The deaths come just a day after that of another mine worker.

"This accident, which happened 2.225m below surface in the Main Shaft, was also caused by a seismic event, with a magnitude of 1.5 on the Richter Scale," the company said.

Their names were being withheld until their next-of-kin had been informed.

"We deeply regret the loss of our colleagues. We remain committed to our quest of achieving zero harm at all our operations. Safety is our number one priority," said Gold Fields's South African operations executive vice president Vishnu Pillay.

Gold Fields chief executive officer Nick Holland extended condolences to the men's families and friends.

"These accidents serve to further strengthen our resolve to eliminate all serious and fatal accidents, and not to mine if we cannot mine safely.

"We are particularly saddened by these accidents as they come after a record 85 days without any fatal accidents on our South African mines.

"Over the past year we have seen a significant improvement in our overall safety performance and with just six weeks to go in this financial year, we have seen our fatalities decline to 16 for the year to date, compared to a total of 47 for the previous year," he said.

The National Union of Mineworkers has condemned Gold Fields's approach to mine safety.