The state highway was re-opened about 3am after a Serious Crash Unit scene examination.
"Officers would like to speak to anyone who may have witnessed the incident or passed by the scene immediately following the crash, and who has not yet spoken to police," a police spokeswoman said.
Another person died due to a crash between a car and a truck in Palmerston North about 12.50am.
The collision happened at the intersection of Napier Rd and James Line, in Whakarongo.
The road was closed for a time while the Serious Crash Unit examined the scene.
A police spokeswoman said inquiries into the circumstances of the crash were ongoing and the death would be referred to the coroner.