Harmony Gold Mining’s Kusasalethu Mine was closed a day earlier than planned for the Christmas holiday after clashes between workers and security guards resulted in shots being fired and damage to mine equipment, The Wall Street Journal reported.

The violence erupted after Harmony suspended 578 workers, including some contractors, for participating in an illegal strike on Dec. 15, Harmony Gold Mining said in a statement.

“We have made it clear that no violence will be tolerated and to ensure the safety of our employees it has become imperative to close the shaft until the labor issues have been resolved,” said Tom Smith, Harmony's chief operating officer, in a statement.

The strike and subsequent violence at Kusasalethu mark the return of the labor unrest that shut down large swaths of South Africa's crucial mining industry earlier this year, damaging the country’s economy and resulting in many deaths.

Almost all striking miners in the country returned to work in mid-November, following a series of pay concessions from their employers, but many industry experts warned at the time that underlying causes of the strikes, such as growing inequality in South Africa and poor living conditions, remained unresolved.

Harmony did not provide any information about the demands of the striking workers on Dec. 15, but said the clashes on Dec. 19 came as workers protested the suspension of some employees who participated in that strike. A spokeswoman for the company said some of the protesters became violent and damaged some surface equipment. They also fired gunshots at security guards who returned fire with rubber bullets, she said.

Five workers were injured in the clashes, the Harmony spokeswoman said.

The Kusasalethu Mine produced 181,105 oz of gold and accounted for about 14 percent of Harmony's total gold output during the financial year ending June 30, according to company reports.

Months of severe labor unrest between August and November badly affected the crucial gold and platinum mining industries in South Africa, weakened the country's economy and created serious political problems for President Jacob Zuma, who was criticized for not doing enough to improve the living conditions of the country's poorest workers.