The Competition Commission said in a statement it had reason to believe staff at the two companies had information relevant to the probe.
“The search and seizure operation forms part of the commission’s ongoing investigation into collusive conduct in the markets for the manufacture and supply of edible oils and margarine to wholesale and retail customers.”
The commission obtained warrants authorising the raids on the offices of Sime Darby in Boksburg and Unilever SA in Durban from the High Courts in Pretoria and Pietermaritzburg.
“During the search the commission will seize documents and electronic data, which will be analysed together with other information gathered to determine whether a contravention of the Competition Act has taken place.”
Acting commissioner Tembinkosi Bonakele called on businesses or individuals to come forward if they had information relevant to the investigation.
Unilever SA spokeswoman Unathi Mgobozi said: “We are co-operating fully with the authorities and are unable to comment further at this stage.”
Sime Darby could not immediately be reached for comment.