A logging truck and trailer has rolled on State highway 4, between Horopito and Erua, leaving one person injured and the road closed.
A police spokesperson said the highway is closed between Tohunga Junction and National Park. The collision was reported to emergency services around 2.50pm.
The driver of the truck was reported to have moderate injuries and had been taken to Whanganui Hospital, police said.
St John sent one ambulance to the crash.
Police said it was expected to take some time to clear the road of debris as heavy lifting equipment was required.
Diversions are in place and motorists were advised to avoid the area if possible, or allow extra travel time.
NZTA said southbound traffic should use SH4 from National Park on to SH47, SH46 on to SH1 at Rangipo. Northbound motorists should take SH49 from Tohunga Junction and then on to SH1 at Waiouru.