Her two female passengers, aged 27 and 28, also from Kaitaia, suffered serious injuries.
One was taken to Kaitaia Hospital by ambulance, and was later transferred to Whangārei with head injuries and broken bones. The other was flown to Auckland Hospital by helicopter with serious head injuries.
Two people in the oncoming vehicle, a small ute, which rolled before coming to a halt in the drain on the other side of the highway, received medical attention for minor injuries. Senior Sergeant Russell Richards said they were receiving victim support.
State Highway 10 was closed between Church and Duncan roads for more than four hours while the Serious Crash Unit carried out a scene examination, reopening around 10pm.
Mr Whiu said a police investigation into the incident had begun, and the Independent Police Conduct Authority would be notified.
Nearby resident Kaye Dragicevich said the driver of the pursued car had tried to climb over the guard rail, but had been apprehended by the police. Her two passengers were lying on the road.
Two ambulances, and later two rescue helicopters, responded. There was no sign of a small dog that had been in the ute, however. Mrs Dragicevich said the jack russell terrier had "scarpered". A boy who had been in a car that arrived soon after the police trying to help find her, without success.
The dog, which was captured on a vehicle's dash cam being ejected from the rear window, landing on its feet and running off, was later seen at nearby cattle yards, where its owners left some toys and a hat. Mrs Dragicevich said she had tried to catch her but could not get close.
"We left food there, and it has returned, but we can't get near it," she said on Sunday.
"I contacted the police but just got Auckland, and so far our details don't appear to have been handed on to the truck owners."
Meanwhile, Mr Whiu urged drivers who were asked by police to pull over to stop.
"Fleeing police can result in serious injury or death, which we are trying to avoid. The risk of not stopping is not worth your safety, your passengers' safety, or that of other road users," he said.