Around 15,000 workers have downed tools in South Africa at a Gold Fields mine west of Johannesburg, just under a week after a strike ended at another part of the same mine, the company said Monday.

“Employees of the west section of the KDC Gold Mine … on the West Rand in South Africa have been engaging in an unlawful and unprotected strike since the start of the night shift” Sunday evening, Gold Fields said in a statement.

“Approximately 15,000 employees are participating in the strike and all production at KDC West has been suspended as a result,” it added.

“At this stage the reason for the strike remains unclear but we hope to gain clarity as soon as possible,” said company head Peter Turner.

A week-long illegal strike by 12,000 workers at the KDC mine’s east section ended on Wednesday. Workers had downed tools in protest against their union leadership.

The Johannesburg strike follows a deadly wildcat strike at platinum giant Lonmin’s Marikana mine almost three weeks ago, which left 44 people dead, 34 of them shot by police in a crackdown. The violence has been blamed in part on union rivalry.

Gold Fields, which is listed on the Johannesburg and New York stock exchanges, produces 3.5 million gold equivalent ounces a year, according to its website.

The company operates eight mines in Australia, Ghana, Peru and South Africa.

[Image via Agence France-Presse]