A vehicle seen driving erratically just minutes before it crashed, killing three people in Hamilton, had driven down from Auckland, police believe.
Waikato police are investigating how the two cars collided on the Hamilton city bypass of Mangaharakeke Dr/State Highway 1 early on Sunday morning.
The crash claimed the lives Auckland teenager Grace Hill, who was turning 17 at the end of the month, who had just moved to Hamilton to live with her boyfriend, Mitchell Kay.
Kay was the driver of the Holden Trax which also had his parents, Jeremy and Tania Kay, as passengers. Kay survived but his parents died at the scene.
Police earlier confirmed a Toyota Prado had been seen speeding just prior to the crash and today Waikato road policing manager Inspector Marcus Lynam said they now believe the man driving the Toyota had driven down from Auckland.
He was in a stable condition in Waikato Hospital with moderate injuries, he said.
"He is believed to have driven down from Auckland, and police continue to ask for anyone who witnessed a blue and grey Toyota Prada driving erratically or at speed, late on Saturday or early Sunday, to come forward.
"The driver of the Toyota is helping police with inquiries. No charges have been laid at this stage."
CIB and the police serious crash unit are working to establish the circumstances of the crash, he said.
"The investigation into the crash is complex, and is expected to take some time.
"We extend our condolences to the families involved, and have offered them support."
The crash has now pushed the country's road toll up to 323, the exact same figure as same time last year. That resulted in a record number of deaths by the year's end.
When asked about the skyrocketing road toll and what's driving them, a police spokesperson said there were four main behaviours that contributed to death and serious injury on the roads; speed, driving while impaired - alcohol, drugs or fatigue - driving while distracted, and not wearing a seatbelt.
"The decisions we make as drivers impact on everybody else on the road as well. So let's all be sensible and keep each other safe.
"What we want people to remember is to drive safely and not take risks."
Meanwhile, Hill's Orewa-based mother, Hayley Ellwood, today spoke out about the loss of her daughter but said it was slowly sinking in.
"She was hilarious. She was determined but the Kay family are absolutely amazing for her so she was just so well looked after and loved.
"She was hilarious, quite a laugh and had a huge group of friends from all walks of life ... and I can see that from all of the messages coming through it's just completely overwhelming."
She named her daughter after the hymn Amazing Grace because she was simply that: amazing.
"Amazing Grace, that's how she got her name. That's my favourite and that's how she got her name and she lived up to that."
However, she was intrigued to learn how the crash happened.
"What can you say. The guy is pretty lucky. He gets to walk away and I don't understand how it happened, we drove past there yesterday a couple of times and I just don't understand how it could have happened.
"But what he's done to our family and the Kay family ... [Mitchell] and his sister are orphans. You just can't get your head around any of that."