Around 16,000 litres of milk was spilt on State Highway 1 after a tanker driver was forced to take evasive action.
The crash happened on State Highway 1 just south of Umawera at around 11.30am on Sunday after a Mangonui Haulage milk tanker driver took evasive action to avoid an oncoming car.
The company was grateful the outcome wasn't a great deal worse.
Mangonui Haulage proprietor Sean Sparksman said the driver was heading south when he was confronted with a car straddling the white line as he negotiated a right-hand bend.
He swerved as far to the left as he could to avoid a collision, but lost control of the fully-laden truck and trailer.
The tractor unit came to a halt hard up against a bank on the other side of the road, with the trailer, which was upended, alongside it.
"He managed to avoid the car but it all went pear-shaped after that," Sparksman said.
The driver escaped without injury, but the trailer would probably be a write-off.
One lane was blocked for a number of hours. The NZ Transport Agency reported stop/go traffic management was in place until the scene could be cleared.
It was "all sorted" by around 5.30pm, Sparksman added, with help from Don Mackenzie, who delivered a crane to the scene from Kaitaia to lift the trailer back on to its wheels.
A Fonterra spokeswoman said the truck and trailer unit was contracted to Fonterra at the time.
She said the entire trailer load of milk, around 16,000 litres, was lost but the truck's load was able to be recovered.
The milk went into a waterway on the neighbouring property and, as a result, Fonterra notified Northland Regional Council so it could investigate and monitor the situation.