Western Cape Traffic Chief Kenny Africa is uncertain when the N1 southbound between Rawsonville Weigh Bridge and Du Toitskloof Pass will be reopened.
On Tuesday morning, the lane heading toward Paarl was closed after a truck carrying hazardous substances caught alight.
"It will take a long time to open the road as it will take time to remove the wreckage.
"The police, the fire brigade and provincial traffic services are currently at the scene," Africa said.
He confirmed that no fatalities or injuries were reported.
Motorists were advised to note the road closure.