The female driver of the campervan was killed and the other person in the vehicle was taken to hospital in a critical condition. They are believed to be foreigners who arrived in the country this year.
A second vehicle was forced to take evasive action and drove off the road into the scrub. The female driver, and only person in the car, was uninjured.
The truck driver lost control and crossed the centre line into the northbound lane and collided head-on with a third vehicle, killing the male and female occupants.
The truck driver was taken to hospital in a serious condition with suspected spinal injuries.
Ewers said police were still trying to find out who the people are and notify their families.A few motorists stopped and helped, including a nurse, before emergency workers arrived, he said.
"We will follow them up and give them support. They will be traumatised.''
He said it was a traumatic experience for police, who had to deal with fatal crashes repeatedly in Northland.
Police were debriefed immediately after the road was cleared and part of that included making sure victim support was offered to the families of the dead.
Police staff would also be given support.
Ewers said road conditions at the time were fine but it was an area known for crashes.
"This piece of road is notorious and people have to take extreme care on it.
"It's a 100km/h zone through here - it's seen many accidents, unfortunately, and another one today that will leave families missing their loved ones."
Diversions were put in place via Maungatapere, Tauraroa Rd and Mangapai. Police advised motorists to avoid the area completely if possible. However heavy vehicles on both sides of the crash were forced to pull over and wait until the road reopened after 4.30pm.
Northland's road toll now stands at 30, compared to 27 for all of last year. With increased traffic expected on the region's roads over summer, Ewers had a succinct safety message.
"Just take care on any road when you're driving and make sure you are aware of the road rules and take extreme care."