File image. Photo: RNZ / Rebekah Parsons-King
Part of State Highway 1 is blocked after a crash involving two vehicles near Sanson in the Manawatū District.
Police said initial indications were that there were serious injuries - one person was taken to hospital in a critical condition.
St John has confirmed it treated one patient in critical condition and an ambulance was taking them to Palmerston North hospital.
Traffic diversions are in place for the incident, south of Fagan Road, and motorists should expect delays.
Waka Kotahi is advising people to avoid the area or use the detour that has been set up.