The death toll of Friday's bus crash in Maraisburg has risen to four, emergency services said on Saturday.

ER24 spokesman Werner Vermaak said the death toll had risen overnight and injured people were being brought to hospital in private vehicles.

Around 80 people were injured when a bus collided with a truck on the N1 freeway at about 6.00pm on Friday.

"Quite a few passers-by took people to hospital in their own cars," said Vermaak.

He urged the public to refrain from this as they may be held liable if the person dies in their care en-route to hospital.

"If the person is bleeding, rather let a professional or trained person look at them before you transport them."

The freeway was closed until early Saturday morning.