"There are 23 people who are injured and two are dead," said Johannesburg EMS spokesperson, Robert Mulaudzi.

Earlier, ER24 said in a statement that at least 17 people were injured, while Netcare 911 said on Twitter that 15 people were injured - five critically.

Mulaudzi told News24 that three vehicles were trapped under the collapsed structure but all the occupants had been extricated from the vehicles.

None of those injured were children.

Murray & Roberts, the company responsible for the construction, said it was probing the incident.

Company spokesperson Ed Jardim said they did not immediately have all the details of the incident, but they had sent people to the scene.

"We have not been able to look at the cause as yet. At the moment, we are concentrating on ensuring that if there are any people injured, they are attended to quickly," said Jardim.

A motorist told Eyewitness News that he saw the structure crash onto the car behind him.

According to an eNCA report, a minibus taxi was trapped underneath.

A photograph shows the red structure, which was reportedly meant to be a pedestrian crossing, blocking both the north and south-bound lanes of the highway.

- News24.com