Amid fears of possible links to mob and Black Power rivalry, the investigation included examining the second vehicle, which left the scene.
It was found several days later in the Raupunga area, after discussions which involved family of those in the second vehicle, lawyers, and other gang leaders.
Police also spoke with those believed to have been in the second car.
They are understood to have later discussed progress with the bereaved families, and met again with families yesterday to discuss the outcome.
Police later also met with community leaders, including deputy mayor Denise Eaglesome-Karekare.
The crash sparked fears of retribution, before police had established what happened, but gang relationships specialist and Black Power member Denis O'Reilly, of Napier, said that, since the initial issues, police had been sensitive and "very thoughtful in looking for a later solution".
Also, "good leaders" of those linked to the families had "worked their way through it".
Wairoa Mayor Craig Little said from Auckland last night he was impressed with both the police and the leaders of both gang groups, who had adopted a "cool-headed" approach, and who he believes want a positive future in the town for their people and their families.
"Perhaps this will end the rumour and the speculation," Mr Little said.