Johannesburg - Prison warders protested outside Mangaung Prison in Bloemfontein on Thursday, the prison said.
The warders, who were employed by a security company, were angry about the suspension of a fellow employee on Monday, said the prison's contract management director Joe Maako.
He said the suspended employee was accused of intimidating and influencing members to protest during wage negotiations.
The protest began on Wednesday.
Only a few of the prison's 400 warders reported for work.
The warders were expected to meet with the security company's management on Thursday, said Maako.