Certain places near Irene in Pretoria were covered in a cloud of black smoke as a truck transporting bitumen caught fire on the R21.
Bitumen, commonly known as asphalt, is used for road surfacing.
The incident happened before 06:00 on Sunday.
"The driver of the truck noticed the truck was on fire and moved it to the side of the road, Tshwane emergency services spokesperson Johan Pieterse told News24.
He said the driver jumped out and was not injured.
Pieterse said the truck was fully engulfed in flames when fire engines arrived at the scene.
He added that the bitumen had melted onto the open grass and they had to "safeguard the houses in the area".
No houses were burnt.
"Bitumen is usually transported warm and at this stage, we don't know the cause of the fire," he said.