More than 500 mineworkers were not allowed into Harmony Gold's Kusasalethu hostels in Carletonville on Tuesday night, a workers' representative said.
"They went out to buy food and when they came back they found that security and police blocked the entrance," Paul Motaung said.
Security guards were only allowing people to go out of the hostels and not letting them back in. He said police were called.
"More than five police vans are here, and when I spoke to them they said they were here for backup."
Some of the workers went to a nearby village to borrow blankets. Motaung said they wanted to camp outside the hostels to support their colleagues who were inside, because they did not know what might happen to them during the night.
Harmony spokesperson Henrika Basterfield said there should be no one at the mine because it was closed.
"All I can say is the mine is closed. Only about a 100 people came to the mine two days ago. Transport was arranged for them to go back home."
She said out of that 100, only seven produced their employee numbers when asked to do so. They were given transport back home. The rest refused to show their numbers and were not helped.
She further said workers were told on December 21 and 31 that the mine would be closed.
"Only that little group came after people were notified about the closure."
On Monday, Harmony Gold said it would keep its Kusasalethu mine closed while it considered whether to continue operations there or begin retrenchments. It said it had started a process under section 189 of the Labour Relations Act, which determines procedures to be followed when retrenching workers.
"Management is of the view that the status quo concerning production and labour strife will remain, as it has exhausted all possible avenues to achieve normal production and cannot find a solution to the current state of lawlessness prevailing," it said in a statement.
In December, more than 1000 employees staged an underground sit-in at the mine demanding that their fellow employees, who had been suspended, be reinstated.