Three ambulances attended and a rescue helicopter from Hamilton also responded.
The St John spokeswoman said three people were taken to Waikato Hospital, two in a serious condition, and another with moderate injuries, and one of the seriously injured patients was flown to hospital in the rescue chopper.
There were no reports of road blockages, said the police spokeswoman.
Rotorua man Thomas Falconer, who witnessed the crash, said everyone seemed to be in a "bit of shock".