St John area manager Tony Devanney said the woman, believed to be in her 40s, died at the scene. The driver of the truck was taken to Whangarei Hospital in shock and was treated for minor injuries.
Northland road policing manager Inspector Murray Hodson said next of kin had not been notified and serious crash investigators were still trying to piece together evidence to determine what had caused the crash.
There was extensive damage to the car and the roof had had to be cut off to remove the woman.
The truck had remained upright but blocked all three lanes, making it impossible to pass. Detours were set up through Maunu Rd and Loop Rd.
Mr Hodson said a significant amount of diesel was spilt by the truck, with bitumen starting to lift off the road.
"You've got roads, you've got diesel, you've got bitumen - it becomes a skating bowl. It's dangerous."
Contractors from Downers spread sand across 100-200m of the road to soak up the diesel, and Mr Hodson hoped to have one lane open for traffic by 6.15pm yesterday, but with a temporary speed limit of of 30km/h, which was enforced overnight.
One motorist who phoned the Northern Advocate, a sales representative travelling back to Auckland, said he had been turned around at Rewarewa Rd and had taken the diversion through Maungatapere, down Otaika Valley Rd and back on to SH1 that took 90 minutes. Another motorist said it took 45 minutes to get from Kamo to his depot in Rewarewa Rd.
Yesterday's fatal crash comes after a 6-year-old boy died near Waipu earlier this month and takes Northland's road toll for the year to 14.
There were 21 road deaths in Northland last year, 12 of which happened between August and December.
