A truck lost its load of liquid carbon dioxide (CO2) as it went around a bend between Te Awamutu and Otorohanga this morning.
Senior Constable Neil Warren said the trailer came loose and rolled down a bank into a paddock.
Nobody was injured in the accident on State Highway 39.
Mr Warren said there was very little danger of the CO2 exploding.
The incident reduced the road to a single lane and a crane was called in to recover the truck and trailer.
Elsewehere a logging truck has crashed just south of Te Awamutu this morning.
No one was injured, Mr Warren said.
- NZPA