A crash involving five cars closed the southbound lanes of State Highway 1, just north of the Tram Road overbridge this morning.

Police were called to the scene on the Christchurch Northern Motorway, between Ohoka Road and Tram Road, at around 10:40am.

St John said three ambulances, one rapid response unit, and one operations manager attended the scene.

In total, seven patients were assessed by paramedics. One patient, who was in a serious condition, was transported to Christchurch Hospital by road.

Three patients with moderate injuries were also taken to Christchurch Hospital by road, while three others, who sustained minor to moderate injuries, were assessed and treated at the scene and did not require transport.

State Highway 1 is now reopened to southbound traffic from the Tram Road overbridge to the Ohoka Road offramp.

Motorists are being advised to avoid the area if possible and to expect significant delays.