Six people were taken to Waikato hospital's emergency department following a three car crash at 11am on Saturday on State Highway One at Horotiu, north of Hamilton.
They are four Japanese people from one car, believed to be students, and an elderly couple from Otorohanga.
Two of the injured are in a serious condition while three of the others are in a stable condition.
The occupants of the third car did not require hospital treatment.
The highway is still partially closed. Detours are in place.