One of the cars involved in Tuesday's fatal Waikato crash crossed the centre line, police have revealed.
Five people died after a head-on crash on State Highway 3 near Te Awamutu.
Speaking to media on Wednesday, Waikato district road policing manager Jeff Penno said evidence from the scene shows one of the cars crossed the centre line, but he said it's still unclear why.
"At this stage, we don't know why it occurred. We know one vehicle crossed the centre line and collided with the other. We know exactly where that happened, and it was clearly across the centre line, but we don't know why," Inspector Penno said.
"We understand the time it happened, where it happened, [and] how it happened but we don't know why it happened."
Inspector Penno added alcohol and drugs are a focus of the investigation and police don't believe road conditions or speed played a factor.
"Impairment is always something we look at... and that is certainly a focus with this accident."
He added the stretch of road where the crash happened is not a "high risk area".
But despite speed not being a factor in this crash, Penno said there are questions over whether 100km/h is appropriate for the stretch of road. Although he said that is a decision for the New Zealand Transport Agency.
Penno also said his heart goes out to the families of this "horrendous event".
"Every fatality on our roads is gut-wrenching for the police," he said. "People died and we've failed. Our job is to keep people safe."
He stressed officers would be out in force over the long weekend and urged people to drive safely.
"If you offend in the Waikato this weekend, you can expect red and blue flashing lights behind you."
Emergency services were called to the crash at 4:44pm on Tuesday.
At the time Penno said sadly five people were dead.
"Emergency services are there working through it, making sure we collect all the evidence, making sure we work through the deceased with respect for them, and trying to establish what has happened at this horrendous crash.
"This is why police do what we do. This is why our partners at NZTA do what they do. To stop this kind of road trauma," he said on Tuesday.
Police said the three occupants of one vehicle, and two occupants of the other vehicle all died at the scene.
