Children aged 10, 9 and 11 were okay, the Fire Service said.
In another crash in Northland, a man died at the scene after a vehicle he was a passenger in left State Highway 1, hitting a tree, near Towai just after midnight.
The male driver was transported to Kawakawa Hospital in a serious condition.
Kaumatua have blessed the sites of both crashes, and the Serious Crash Unit continues to investigate the cause of each incident.
Northland Duty Inspector Riki Whiu said: "Our condolences and thoughts go out to the local families of those who have died in these tragic incidents.
"Any death on our roads is a tragedy, and it's especially difficult for all of our staff to have two fatal crashes in the space of one night.
"Police wish to remind those travelling on our roads, in particular in such terrible driving conditions, to drive to the conditions and look after each other."
Both crashed have been referred to the coroner and next-of-kin are being notified.
One person died after a crash south of Waiouru this morning on State Highway 1.
The single vehicle crash happened just before 5.45am about half a kilometre south of Springs Hill.
In Auckland, a motorcyclist died early this morning trying to flee from the police in a chase.
The driver refused to stop for police when the bike was seen travelling at speed about 1.15am in Mt Albert.
The motorcyclist failed to take the Royal Oak roundabout and fell off the bike, hitting a parked car.
Police are investigating and the Independent Police Conduct Authority has been advised.
A fifth man died after the car he was driving hit a power pole in Taranaki yesterday afternoon.
The crash happened on Ketemarae Road, Hawera about 4.15pm.
The victim was the sole occupant of the vehicle and there were no other injuries, police said.
Diversions were in place while the road was closed and the accident scene cleared.
Several people were injured in crashes around the country today.
Emergency services are attending a two car crash in Warkworth, Auckland, a police spokesman said.
One person was critically injured during the crash, which happened on SH1 near Auckland Rd and Toovey Rd just after 3pm.
Three other people are in a serious condition after a two-car crash on SH2 between Tauranga and Waihi yesterday.
This morning a woman escaped with minor injuries after crashing into a building in Onehunga, Auckland.
And a driver suffered minor injuries this morning when a car crashed into a barrier on Auckland's North Western motorway.
National manager road policing Superintendent Steve Greally said any death or injury on the roads was "one too many".
"Everyone - including road users - need to do their part to reduce deaths and injuries on our roads and in our communities right across NZ.
"Police cannot do it alone. Road safety is everyone's responsibility.
"Education and Police enforcement is just one aspect of keeping the roads safe. The driver and the decisions they make are also an important part of the picture.
"Making smart decisions on the road can be done by following the basic road safety rules."
He reminded drovers to check their speed, drive the conditions, avoid alcohol, take rest breaks and always wear seatbelts.
He said: "Not all roads are created equal - many of New Zealand's roads are unforgiving and leave no room for mistakes.
"Many of our rural roads are not five star roads and our bodies are fragile. The speed limit is the maximum speed you can travel at safely in ideal conditions. Often a strip of paint is all that separates you from oncoming traffic.
"If you crash - regardless of the cause or who is at fault - speed is the single factor that most affects the outcome. Just a few kilometres per hour can be the difference between avoiding a collision - or a crash with a tragic outcome."
