Three buses were set alight on Tuesday morning at Ditloung village near the Medupi power station, Limpopo police said.
“Around 1am, it was found that three buses used to transport workers to the power station were burning,” Lt-Col Ronel Otto said.
Police were investigating the cause of the fires. No one was injured and no arrests had been made by 11am.
On Thursday last week, about 80 workers contracted by Murray & Roberts Construction and Grinaker-LTA damaged several vehicles and some equipment at the power plant.
The workers went on protest because the contracts of around 600 local employees were due to end.
Otto said four people were arrested for intimidation on Tuesday morning in Lephalale village, where Medupi is situated.
Police confiscated a vehicle, a banner and a loud hailer from protesters.
There were no reports of violence.
“At this stage the situation is quiet, and under control,” Otto said.
Police were keeping watch. – Sapa