Sergeant Tai Patrick, of Northland police, said the Serious Crash Unit was on-site examining the scene.
A section of SH1, between Mountfield Rd and Rosythe Rd, is closed while they carry out their investigation.
Patrick said traffic is being diverted down both Mountfield Rd and Rosythe Rd but he recommended motorists either avoid the area or delay their journey if possible.
A motorist near the crash site said traffic was steadily moving, except for around 25 freight trucks that were waiting for the road to re-open.
Today's fatal crash is the third to occur in the last week in Northland. It takes the region's road toll to 31 for the year.
David Lewis Charles Collyer, 32, of Dargaville, died last Thursday when the motorbike he was riding collided with a car on Ranfurly and Plunket St in Dargaville.
The following evening another person lost their life on the region's roads when their car crashed off Punakitere Rd in Taheke and then caught fire around 8.15pm.
Police have not yet released the person's name.