The company said workers were taking part in an illegal strike at its northwestern Rustenburg operations and threatened legal action if they did not return to five mines, where unrest forced a temporary shut down.

Amplats said any of its 24,000 workers who failed to return to work by Thursday night they would be considered to be participating in “illegal industrial action” that violated a court order obtained last week.

The company did not specify what legal action it could take, but legislation governing unprotected strikes in South Africa gives employers the right to dismiss strikers.

The five mines were reopened Tuesday after a government crackdown on growing unrest in the key industry, with Amplats announcing a temporary halt last Wednesday as workers protested over wages.

Police arrested 22 people on Wednesday and fired rubber bullets and tear gas in new protests at the platinum giant’s operations.

“The increase in police visibility and action has created an environment conducive for our employees to return to work and isolated incidents of intimidation and violence are being dealt with,” the company said.

The Rustenburg platinum area has been rocked by protests since a deadly wildcat strike snowballed out of the world’s number-three producer Lonmin last month. The firm sealed a wage hike deal with strikers late Tuesday.