Police are at the road bridge in Murray Bridge following a traffic incident on Wednesday morning, September 15.
Emergency services were called to the Eastside end of the bridge about 11.30am, after receiving a report that a trailer had "come off" its towing vehicle while on the bridge and hit another vehicle.
An SA Police spokeswoman confirmed the vehicle driving behind the trailer had been the one to collide with it when it became unhitched.
She said no one was injured in the low-speed collision.
Police are at both ends of the bridge managing traffic, as one lane is currently closed while the scene is cleared.