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.
SH1 SANSON, MANAWATŪ-WHANGANUI - SERIOUS INCIDENT - 12PM, FRI 17 NOV
— Waka Kotahi NZTA Central North Island (@WakaKotahiCNI) November 16, 2023
A serious incident has been reported to emergency sercvices south of Fagan Rd and the road is now CLOSED. Please avoid the area or use an alternate route. ^EH pic.twitter.com/XS5jX8mNUg