Emergency services were alerted to the collision at Piarere, near Tirau, around 5.30am.
Two people were critically injured and a further three people were seriously injured in the two-vehicle crash.
State Highway 1 closed for around six hours while a scene examination took place.
About 9.30am, a car transporter and trailer drove around workers at two cordons and then through the crash scene.
An officer was forced to jump out of the way as the truck and trailer carried on through the investigation area, knocking over cones as it did so.
Senior Sergeant Murray Hamilton said charges were being considered against the 53-year-old Auckland man.
"It doesn't matter if you don't want to take a detour or are running late, there's no excuse that justifies ignoring road closures or putting people at risk.
"Closing a State Highway isn't done lightly or without good reason and in this case, it was to determine what caused a serious crash that sent five people to hospital.
"Thankfully, the majority of people understand that."
Enquiries into the cause of the crash continue.
