The crash happened on a long straight section of State Highway 1 in Taihape.
State Highway 1 has reopened following a serious crash in Taihape that closed the highway this morning.
Four people were hurt in the two-vehicle crash, which happened just after 8am between Gorge Rd and Rauma Rd, south of Waiouru.
Police were called around 8.10am, a police spokeswoman said.
The road was closed for around two hours but has now reopened.
Motorists have been asked to take care passing the crash scene and should expect delays. Traffic management is in place.
The Serious Crash Unit has been advised.
A St John spokesman said four people were injured in the crash. One was helicoptered to Palmerston North Hospital in a serious condition, while a second with moderate injuries was taken to Palmerston North Hospital by ambulance.
A person with moderate injuries and one with minor injuries were both taken to Whanganui Hospital by ambulance.
The circumstances around the death are being treated as unexplained.