An arson attack in the early hours of Sunday morning led to six trucks being set alight on Van Reenen's Pass, which caused the closure of the N3 toll route.
The attackers fled the scene.
"All authorities and emergency services are on scene. They have secured the area, and the fires have been doused. The clean-up and recovery operations are under way," the operator said.
Motorists were urged to delay their trips if possible.
Northbound traffic, heading to Johannesburg, was stopped at Tugela Plaza, while southbound traffic, heading to Durban, was stacked at the top of Van Reenen's Pass.
FleetWatch magazine said the attack was a deliberate "hit".
"After talking to various people on the scene, this was a well-planned attack on trucks. They planned the ambush, got the trucks to stop by spreading some debris and rocks across the road, shooting at them and then burning them.
"One truck has numerous bullet holes in the cab from the attackers shooting at it."
TimesLIVE
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