State Highway 7 near Balmoral in the Hurunui District is closed, following a serious crash involving two vehicles.

A police spokesperson said the crash was reported to police shortly before 1.30pm.

One of the vehicles was reportedly upside down.

Emergency services are at the scene and one person has been seriously injured.

The police spokesperson said a horse float was involved and the horses are being assessed by a vet.

Diversions are in place and motorists are advised to avoid the area and expect delays.

A Westpac rescue helicopter has been called to the scene, along with local Fire and Emergency crews.

NZTA said due to the crash near Long Plantation Road, the road is down to one lane under STOP/GO.