"For whatever reason [the front car] has lost control and crossed the centre line," he told 3News.
The road was blocked for more than three hours while firefighters and tow truck drivers worked to clear the wreckage. Traffic used a detour until the road was reopened at 6pm.
The crash follows a series of accidents in which a total of eight people died and at least six were injured.
In Waiatarua, West Auckland, a woman lay trapped in her car after driving off a steep drop hidden from the road.
Just before midday, she called emergency services on her cellphone and crews from two fire trucks found her on Forest Hill Rd and cut her from the wreckage.
She was taken to Auckland Hospital in a moderate condition.
On Saturday night about 6pm an elderly female pedestrian was hit by a car on Mt Albert Rd and died at the scene.
An 18-year-old driver, the sole occupant of a car that crashed into a tree in Te Puninga in the small hours of yesterday morning, was in a serious condition.
Sergeant Thomas Smart said the driver had been at a social gathering before driving and failed to navigate an intersection.
A 16-year-old suffered a serious leg injury after falling from his motocross bike during racing at Foxton. He was airlifted to Palmerston North Hospital.
Police yesterday named the rally driver who died in a crash near Hanmer Springs on Saturday afternoon as Royce Watson, from Christchurch. The 54-year-old had just crossed the finish line on the first forest stage when he crashed into a tree.
He died at the scene, while his 23 year-old co-driver is in a serious but stable condition in Christchurch Hospital with head and back injuries.
Investigations by police and the Ministry of Business Innovation and Employment are continuing.
Yesterday afternoon, the fourth man involved in a fatal crash after a police pursuit on Friday night died.
Viane Gaga's ventilator was turned off on Saturday night and he died yesterday afternoon, a Counties Manukau spokeswoman said.
His three friends, George Lomia, Dominic Stehlin and Uesetini Tootoo, also died after their vehicle hit a parked car on Massey Rd just before midnight. A friend of the Gaga family earlier said family members had gathered at his bedside to pray for him and to say their goodbyes.
Mr Gaga had been in bed on Friday night when his three friends, all De La Salle College old boys, dropped by his Mangere home, where he lived with his parents, and asked him to go out for a drink.
Read more: Lack of police pursuit 'turns roads over to criminals'