Murray & Roberts, the company responsible for the construction at the M1 highway where a temporary bridge collapsed on Wednesday, 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.
He said the company would be issuing a statement shortly. It was unclear how many people, if any, were injured in the incident.
Reports from the scene are that at least one vehicle was trapped after the pedestrian bridge collapsed. 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.
It was unclear whether any people had been on the bridge at the time.
Netcare 911 spokesperson Chris Botha told News24 paramedics were on the scene, and would provide information soon.