One vehicle has since left the scene.
Witnesses reported that an elderly driver was trapped in the flipped vehicle but was removed safely.
Police described the worst injury as moderate, with no life-threatening injuries reported.
A Herald reporter at the scene said traffic was heavily affected in the area, with congestion extending to nearby roads and the motorway.
A tow truck has been called in.
Ben Tomsett is a multimedia journalist based in Dunedin. He joined the Herald in 2023.