A male driving instructor is in a critical condition after the car his student was driving collided with a truck on the outskirts of Te Awamutu.
The instructor, a passenger in the car, was trapped in the wreckage after the crash on SH3, just north of Taylor's Hill at about 10.35am.
He was freed by firefighters before being taken by ambulance to Waikato Hospital.
The truck driver and learner driver were both taken to hospital for assessments.
Police say it appears the teenage girl driving the car lost control before the crash.
They want to speak to a motorist who stopped to speak with the distraught teenager after the crash before driving off.