Three children aged 10 to 13 were the only occupants in a car that lost control at high speed and rolled down a 4m bank in Waikato this afternoon.

The Waikato Westpac Rescue Helicopter was called to the scene at Ohinewai, north of Huntly, this afternoon.

A helicopter spokeswoman said rescuers found three children in the vehicle - a 10-year-old boy and two 13-year-old girls.

An underage driver had lost control at high speed and the car rolled.

All three were taken to Waikato Hospital - the two girls by ambulance and the boy in the helicopter.

"The incident is under investigation. The helicopter was dispatched due to the severity of the crash and initial reports that the victims were trapped," the spokeswoman said.

A Fire Service spokeswoman said two fire trucks were dispatched to the scene just after 3pm, as was normal in motor vehicle crashes.

But nobody was trapped and they weren't required.