State Highway 1 has been blocked in both directions south of Hampton Downs, near Te Kauwhata, following a four-car crash.

Police were notified of the incident around 3.45pm and initial reports suggest four people have been injured.

The incident occurred between Whangamarino Rd and Wayside Rd and the New Zealand Transport Agency says contractors are en route.

Motorists are being asked to avoid the area if possible.

Southbound traffic is being asked to divert onto Hall Rd, meanwhile northbound traffic has been asked to exit SH1 on Plantation Rd.