Medupi power station remained closed on Tuesday, following a protest by Eskom contract employees last week, engineering group Murray & Roberts said.
Spokesman Ed Jardim said that operations at the power station were put on hold on Friday, although no violence had been reported since then.
“The safety of the labour force, as they are not on site, is not being impacted.”
It was unclear when operations would resume at Medupi.
On Thursday last week, about 80 workers contracted by Murray & Roberts and Grinaker-LTA damaged several vehicles and some equipment at the power plant.
The workers began protesting because the contracts of about 600 local employees were due to end.
Earlier, police spokeswoman Lt-Col Ronel Otto said buses were burnt at Ditloung village near the Medupi power station early Tuesday morning.
“Around 1am, it was found that three buses used to transport workers to the power station were burning.”
Police were investigating the cause of the fires. No one was injured or arrested.
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 by 1.30pm.
“At this stage the situation is quiet, and under control,” Otto said.
Police were keeping watch.
Medupi, a 4764MW power station, was expected to start generating power for the national grid next year. - Sapa