Emergency services are at the scene of a crash involving two cars and a truck on State Highway 1, Hunterville.
Police were called about 9.50am.
One person has died following the crash.
Traffic management will be in place while the Serious Crash Unit examines the scene.
Light vehicles are being diverted down Jeffersons Line and Leedstown Road, heavy vehicles up to 50 tonnes will need to use SH4 between Whanganui and Raetahi, and for larger vehicles there will be significant delays.