The N1 between Verkeerdevlei and Winburg remains closed for traffic while a cleaning up operation is underway.
In one of the trucks, both the driver and his co-driver were killed. Officials say the diesel spillage is taking longer to clean up.
Vehicles travelling on the N1 from Bloemfontein are being diverted to the Karee Dam offramp with traffic from Winburg being diverged to the Brandfort road.
Emergency Medical Services (EMS) Spokesperson, Sipho Towa says the police are still investigating the cause of the accident.
Mangaung Fire Services says they are cleaning the area.
“They are busy with clean up and after clean up they will also do spillage clean up. What’s taking long is because of the diesel spillage at the scene. So we urge road users to be patient and to follow the diversion rules as directed by the law enforcement agencies.”