Seven trucks were set alight by unknown suspects in the early hours of Thursday morning on the N3 between Mooi River and Estcourt.
KwaZulu-Natal police spokesperson Thulani Zwane told News24 that it happened just after midnight.
"The trucks were set alight by unknown people who were threatening the drivers. They told the drivers to get out before, and then they set alight the trucks."
Zwane said a case of public violence has been opened at the Mooi River police station.
The N3 between Mooi River and Estcourt remained closed on Thursday morning.
"No one has been injured and no arrests have been made," Zwane said.
"We don't know what the motive was."
Zwane said traffic is being diverted to other routes.
This is a developing story.