State Highway One reopens after serious crash involving caravan north of Auckland

State Highway One has fully reopened after a serious crash involving caravan north of Auckland this afternoon.

Police say emergency services were called to the crash just south of Wellsford at 1pm.

St John say a woman was critically injured and has been airlifted to hospital.

Three other patients, one in a moderate condition, and two others with minor injuries have been transported to North Shore Hospital.

Part of State Highway One was closed and motorists were being asked to avoid the area if possible.

The NZ Transport Agency say the road has now reopened in both directions.