A bus carrying passengers caught fire on the N1 highway north near William Nicol Drive on Wednesday morning.
Johannesburg metro police spokesperson Wayne Minnaar said the bus was travelling from Cape Town to Zimbabwe.
Pictures of passengers escaping through the windows have been widely circulated on social media.
“There have been no injuries reported. It is only the luggage burning,” Minnaar said.
He said emergency services were on the scene battling the blaze.
Traffic was heavily backed up for kilometres around the area and motorists were advised to use alternative routes.
Shawn Herbst of Netcare 911 said they were alerted just before 7am. “Reports from the scene indicate that a bus had caught alight, setting fire to the trailer. Fortunately the passengers and crew managed to escape just before the entire bus was engulfed in flames.”
Describing the scene, he said: “The area around the bus was littered with baggage as passengers scrambled to retrieve whatever belongings they could.”
The cause of the fire is under investigation.
The transport ministry described the incident as “an absolute tragedy”.
Ayanda Allie Paine, ministry spokesperson, said the bus was carrying 44 passengers, mostly women and children.
“Thank goodness there were no injuries or fatalities, but the passengers lost everything they had saved up for and bought for their families back home.
“The passengers have been left destitute. They will be going home with nothing but the clothes on their backs.”