The three who died in the crash on State Highway 1 in Auckland yesterday were in the van and were killed on impact, Inspector Tony Wakelin told media at a press conference today.
They were 45, 37 and 32 years old, he said.
The other three people in the van were taken to hospital, where a 21-year-old male remained in a critical condition and two other men aged 42 and 39 had moderate injuries.
Wakelin said formal identification was continuing but those in the van were seasonal workers due to return home to Samoa later this week.
"The truck driver was treated for minor injuries and has since been discharged from hospital," he said.
"This was a horrific crash and we're continuing to provide support for everyone affected, including our staff who attended the scene."
"It's indescribable ... Our staff are sadly, used to attending these sorts of incidents but when it gets to this sort of magnitude and this number of people involved, the number of fatalities, and the extent of the injuries, it's a really horrible for them to attend."
Anyone who witnessed the crash or had videos of it on dashcams was being encouraged to get in touch with police.
"Every single element, including road factors, driver's factor, vehicles, everything that forms the final outcome of the crash will be investigated to the nth degree and if there's any learnings from that, or any culpability, then that's something we'll be bringing to our investigators," Wakelin said.
He applauded members of the public who jumped in to help, but he was highly critical of people who had filmed the aftermath of the crash.
"I thought that was disgusting. It really was. I saw some of the footage. It was filmed before emergency services arrived," he said.
"I say to the people who were doing that: 'How would you feel if that was your family?"
