A Northland mother and her toddler were killed while her other child was seriously injured when their vehicle and another car collided head-on.
Early police investigations revealed a 20-year-old mother from Kaiwaka, her two children - both aged under 3 - and a man were travelling north when the crash happened on State Highway 1 about 200m north of Oruawharo Rd in Topuni about 9pm on Saturday.
Two people heading south were in the other vehicle involved.
The driver of the southbound silver sedan then allegedly failed to stop and was located just north of Auckland with another person who was in the car at the time of the crash.
Police have laid two charges of driving with access breath alcohol causing death against a 19-year-old man. He is due to appear in the North Shore District Court today.
Further charges are possible, police said.
The seriously injured man in the northbound car was airlifted to Auckland City Hospital by the Auckland Westpac Rescue Helicopter.
A toddler was flown to Starship children's hospital, also in a serious condition.
Diversions were put in place through Mangawhai and SH1 in Topuni was closed until 3am yesterday.
The police serious crash unit have examined the scene and police are investigating the cause of the crash. They are appealing for witnesses.
Detective Sergeant David Hamilton said people driving on SH1 on Saturday evening, particularly in the Maungaturoto and Kaiwaka areas, who saw the silver sedan before the crash are asked to contact police.
Five fire appliances from Kaiwaka, Wellsford and Warkworth attended the scene and helped with traffic control and extracting the bodies.
It is understood a former firefighter, a nurse and a member of the public administered CPR on a critically injured passenger while waiting for paramedics to arrive.
Kaiwaka fire chief John Bowmar said it was not raining when firefighters arrived at the scene.
He said fire crews were initially called to a crash on Dome Valley before they were rerouted to Topuni.
On February 17, a mother and daughter died in a single-vehicle crash on Whangārei Heads Rd after the car they were travelling in left the road on a moderate bend and slammed into a tree.
Sorine Hanham, 30, died shortly after the crash and her daughter, back-seat passenger Niquisher Sanders, 7, died the next day in Starship.
It was the second road fatality in Northland involving a mother and her child this year and the latest serious crash has pushed Northland's road toll to 11 compared with 15 at the same time last year.
Of the 11 fatalities so far in Northland, four involved motorcyclists.
Before Saturday's double fatality, two motorcyclists died in separate crashes on March 16.
A car and a motorcycle collided on State Highway 12, between Taheke and the Rawene turnoff, near the junction with Duddy Rd in Omanaia.
The crash happened when the motorcyclist, a 46-year-old Northland man, tried to overtake the car on a bend.
The motorcyclist died at the scene, while the male driver of the car suffered serious injuries and was flown to Auckland City Hospital.
In the other crash, a 63-year-old motorcyclist from Auckland hit the side of a bridge on Tangowahine Valley Rd.