Mopping up this morning's offal spill between Woodville and Dannevirke was not going to be a pretty job, contractors said.
The mess of blood, fat and discarded pieces of butchered animals spread 15km, and was up to 30cm deep in parts after a tailgate opened on a truck.
Commuters were asked to take a 10-minute detour, as the section of State Highway 2 was closed for the clean-up between Condoit Rd and Maharahara Rd.
A report that a car had skidded and crashed at the spill alerted police to the situation.
New Zealand Transport Agency contractors on the job said it was a "pretty bloody awful" scene, with animal heads and carcasses among the mess.
"It's not really a good day for my boys," a spokesman said.
"Offal spills have a huge amount of fat in them and that poses a risk to the public so we closed the road."
The contractors intended to pick up the worst bits with loaders, use a biodegradable detergent and put a crusher dust (similar to sand) on top of it. It could be "a bit ripe" for the next few days as there was likely to be some residue.
NZTA state highway manager Errol Christiansen said they were looking for a suitable dumpsite and the road was likely to be closed until noon.
Volunteer firefighters were called to the scene but not required.
Police are warning road users to wash their vehicle thoroughly to avoid infection.