A Fire Service spokesman said one person - believed to be the dead man - was trapped in a van.
Senior Sergeant Darryl Lennane said inquiries into the cause were continuing.
A second person died at the scene of a single-vehicle crash in Waiuku, south-west of Auckland.
Police were notified of the incident on Kairoitahi Rd at 5.20am, Inspector Kerry Watson said.
And a young man who died in Hamilton last night was not wearing his seatbelt at the time of the crash, police said.
Emergency services were called to Hall Rd, in the suburb of Frankton, about 11.30pm.
It appeared a Honda hit a kerb and a small wall before colliding with a large signpost and stopping, District Road Policing Manager Inspector Freda Grace said.
The sole occupant, a 25-year-old man, died. He was not wearing a seatbelt and speed may have been a factor in the crash, Ms Grace said.
The road is "well-lit" and "fairly straight" and conditions were good last night, she said.
The fourth death involved a quadbike crash on a Waikato farm this morning.
Details about the victim - including gender and age - were yet to be released by police, but a spokesman said emergency services were called to the farm near Chartwell about 5.45am.
The farm was on Puketaha Rd, near the intersection with Seddon Rd.
A St John spokeswoman said paramedics were called but the patient was dead on arrival.
WorkSafe New Zealand had been notified.
Meanwhile one person was airlifted to hospital in a serious condition after a crash involving a stolen car in Northland early this morning.
Two cars collided about 5.20am outside the phosphate factory near Kaiwaka.
