A contractor working at Camden power station in Mpumalanga was arrested on Tuesday after being positively linked to an incident of sabotage. 

The contractor admitted to intentionally removing the oil drain plug from a bearing on Thursday last week, causing oil burners to trip repeatedly, Eskom said in a statement.

The worker was employed by a maintenance company working at the power station, and said his employer was promised additional maintenance and repair jobs at the power station if he carried out the task.

The arrest followed "intensive investigative work by Eskom teams", the power utility said on Wednesday. While the contractor was arrested, no details were provided of Eskom employees that may have been involved in the promising of additional work.

"This malicious act caused all the oil to drain out from the bearing, thus damaging [it], which in turn prevented the mills from operating optimally," Eskom explained. The incident caused Camden Unit 4 to trip due to the mills not functioning.

A case of sabotage was opened at the Ermelo police station.

"Intensive internal investigations led to the culprit being identified and questioned about the incident. The evidence obtained, and the confession made by the perpetrator revealed that the plug was intentionally removed to cause the trip. This act of sabotage would ensure that his employer was awarded additional maintenance and repair jobs at the power station," Eskom said.

Advocate Karen Pillay, general manager for security at Eskom, described the situation as "disheartening".

"We have always suspected that some of our maintenance contractors and employees are behind these acts of sabotage. We shall continuously work with the law enforcement agencies to bring these insiders to book and ensure that justice is meted out, but most importantly that those with similar tendencies across Eskom are arrested and removed from the organisation," Pillay said.

Eskom has been attempting to identify and root out ongoing sabotage as it battles unprecedented load shedding. It has also been trying to improve management and has controversially suspended managers at some underperforming plants.

It has also said efforts to tackle ongoing harm dating back to the state capture era – including investigating whether there are still implicated individuals working at the entity – are ongoing.