The Association of Mineworkers and Construction Union (Amcu) says Harmony's Kusasalethu mine in Carletonville needs to take full responsibility if the five trapped miners are not found alive.
Amcu's Gauteng West health and safety chairperson Nathi Mathunjwa said, at the time that the miners went down, the traveling wheel support was not up to the mine's standard.
"The temp pressure there [underground] was above the 32.5 degrees and it is suppose to be 31 degrees. The employees were not suppose to be allowed to work on that particular place."
Mathunjwa said they would hold the mine responsible if the miners were not found alive, saying the Mine and Safety Act says it is the duty of the employer to ensure the working area is safe.
He said the situation at the mine remained the same and that there was still no sign of the trapped miners.
When asked if they remained hopeful that the miners were still alive, Mathunjwa said: "Yes, but we are not going to say so, because the place is so confined, because we don't know if they are still alive."
The five miners became trapped behind a rock wall after a tremor, measuring 1.2 on the Richter scale, caused sections of the gold mine to collapse around 10:30 on Friday.
Rock falls hampered rescue operations.
The cause of the tremor has not yet been established.
Roughly 3 000 miners were working there at the time of the tremor.
No other injuries were reported.
harmony spokesperson Marian van der Walt said on Saturday that all parties had a responsibility to ensure safety at the mine.
"We will conduct a thorough investigation into the cause of the incident once all the employees have been brought to safety."
All mining activities has since been suspended, except for the rescue operation.