The Police Dive Squad have recovered a truck from the Whanganui River after the vehicle plunged into the water on the first hour of Christmas Day.
Police have confirmed one person, a male, was found inside.
"Indications are he was the sole occupant. Enquiries into the circumstances of the crash are ongoing," police said in a statement.
"Police would like to speak with anyone who witnessed the crash or who has information that may be of assistance."
Anyone with information can get in touch with Whanganui Police on (06) 349 0600. Information can also be given anonymously via Crimestoppers on 0800 555 111.
Whanganui District Council announced earlier this morning local iwi had imposed a rahui, a ban on fishing and using the river, which would likely be lifted on December 27.
Such measures are often enacted after someone has died.
Emergency services were called to Victoria Ave Bridge near Anzac Parade in Whanganui about 12.21am after reports a car went into the river, a police spokesman said.
The truck became submerged in the river.
The Police Dive Squad arrived on site about 1pm.
An emergency services staffer at the scene said it was "a sad start to Christmas".
Local iwi have imposed a rahui. A ceremony was held mid-morning.
The crash location has been the scene of previous accidents in 2007 and 2010.
Meanwhile, a person was taken to hospital in critical condition after a crash on Main North Rd in Canterbury about 1.30am.
A police spokeswoman said it appeared a car went through a fence into a field.
The Serious Crash Unit had examined the scene and inquiries were ongoing, she said.