Police have confirmed they were called to a two-car and truck crash near Flock Hill Lodge near Christchurch around 2pm.
The crash happened on a bend on West Coast Rd, 5km west of Flock Hill Lodge.
St John have sent a helicopter to the scene to airlift one patient to Christchurch Hospital in a serious condition.
Two ambulances and a First Response Unit are transporting three more patients in a serious condition and one patient in a moderate condition by road to Christchurch Hospital.
The NZ Transport Agency has advised the road is closed.