Medupi under control: police
No incidents were reported on Wednesday morning at Ditloung village near the Medupi power station where workers are protesting, Limpopo police said.
"The situation is calm and under control at the moment. There were no reports of violence throughout Tuesday night," Lt-Col Ronel Otto said.
Three buses used to transport workers to the power station were set alight around 1am on Tuesday.
Police were investigating the cause of the fires. No one was injured and no arrests have been made.
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.