One person's died and many others are injured - after a crash between a bus and a car in Waikato - on State Highway One between Tirau and Piarere

St John says 13 patients have been flown or driven to hospital - from the collision near the intersection with Paparamu Road.

Two are in a critical condition, four have serious injuries, and seven are moderately injured.

Reporter, Maryana Garcia, is there and says she's seen nine ambulance vehicles and a Westpac helicopter at the scene.

She says it indicates the crash is severe - with authorities and cordons still present.