Trucks and two buses were among the vehicles involved in a collision which left four people dead on the N1 highway south of Johannesburg on Sunday morning.
At least 20 other people were reported to have sustained injuries in the accident which happened on the highway between Grasmere toll plaza and the N12.
"ER24 personnel, along with several other services, arrived on the scene at 07:33 to find numerous vehicles - including light motor vehicles, trucks and a bus - scattered along the road. Numerous patients were found either lying between the vehicles or walking around on the scene," said ER24 spokesperson, Russel Meiring.
"Local authorities closed off the highway while emergency personnel began to assess the patients. Assessments showed that four people had sustained fatal injuries while at least 20 others had sustained injuries ranging from minor to critical."
Meiring said some patients were treated on the scene while the critically injured ones were provided with advanced life support interventions before they were transported by various services to nearby hospitals.
"It is believed that smoke from a nearby grass-fire played a contributing factor in the cause of the collision. Local authorities will be investigating further," he said.
City of Joburg metro police Chief, David Tembe, took to Twitter warning motorists of the same accident. "Fatal accident involving multiple vehicles on the N1 South at Grasmere near the Engine Filling Station. @JoburgMPD & @CityofJoburgEMS are present at the scene, please exercise extreme caution when approaching," Tembe tweeted.
Metro police spokesperson Wayne Minnaar said two men and two women were killed.
He said four trucks, two buses, four cars and two mini buses were involved in the accident.