They are asking anyone with information to contact a crash investigator, Constable Amy Weston, on 09-2156118, or provide details anonymously to Crimestoppers on 0800-555111.
The two boys, who were travelling in the Honda, are meanwhile reported to be in stable conditions at Starship.
So are two remaining patients at Middlemore, from where at least two others have been discharged.
The condition of the fifth patient taken there by ambulance is unclear, as Middlemore believes that person may have been transferred to
Auckland City Hospital.
According to the police, there were five occupants of each car, including children aged seven and 15 in the Mazda.
A man who arrived at the crash site while four ambulances and two helicopters were ferrying the victims to the hospitals said the Mazda and Honda were "absolutely annihilated" after spinning around and becoming wedged parallel to one another in a hedge.
Nearby resident Michael Montgomery said the bend was renowned for its crashes, including the 2009 collision, and became slippery in wet conditions such as yesterday's.
He said the recommended speed limit for the bend was raised from 65km/h to 75km/h after the 2009 crash, to the amazement of residents.
"They [the authorities] astonishingly increased the speed of the corner, which is bizarre, after that crash," he told the Herald.
He was unaware of any improvements made to the road.
Another neighbour said the more recent opening of a landfill on a lane intersecting the bend meant trucks left a considerable amount of loose gravel on the road.
Additional reporting by Sophie Ryan
