“We hope to find answers on what could have been done to prevent the accident,” National Union of Mineworkers (NUM) deputy president Piet Mathosa told reporters.
He said the union would work with the company to find answers.
On Tuesday around 6pm a fire broke out on level 192, about 1733 metres underground.
Nine people were still unaccounted for on Wednesday afternoon.
“We are worried and pray for the nine people that are unaccounted for,” Mathosa said. He hoped the nine would be brought to surface alive.
“In a time like this we are calling for calmness and co-operation. The most important thing is that we find the workers that are trapped underground,” Mathosa said.
Eight miners were rescued from the mine on Wednesday. They would be under medical observation for 24 hours, chief operating officer Tom Smith said.
Eighteen people were reported missing at the end of the shift on Tuesday night. One miner surfaced in the early hours of Wednesday morning. He gave rescue workers the location of his colleagues underground, Smith said. Afterwards eight people were found in the underground refuge bay.
Smith said the fire could have been started by a seismic event which measured 2.4 on the Richter scale. This led to a fall of ground and could have damaged electric cables, causing the fire. The company was however still investigating the cause of the fire.
Ten rescue teams were searching for the missing workers and operations at the mine had been suspended.
When asked about how much money the company had lost, Harmony chief executive officer Graham Briggs said the company’s biggest concern was finding the missing miners alive.
“Our biggest concern is to recover the miners, that’s our priority,” Briggs said.
The fire has been contained.