The N3 Toll Route in the area of Van Reenen's Pass is closed for traffic after, six trucks were set alight on Saturday night.
According to Kwazulu Natal Police, the drivers were stopped by a gang of armed men, who instructed them to exit their vehicles, before setting it alight.
The toll route's operations manager, Thania Dhoogra, says the arsonists fled the scene and are still at large.
She says authorities and emergency services have secured the area and a clean-up operation is underway.
The reason for the attack is not yet known and will form part of a police investigation.
Van Reenen detectives are investigating a case of malicious damage to property.
