Whangarei police investigating the discovery of a woman's body in a central city stream are talking to a 29-year-old local man.

The woman's body was found in Waiarohia Stream about 4.20am on Friday and cordons remain around the area near Tawera Road and Porowini Avenue.

Detective Senior Sergeant Dene Begbie says the man and woman knew each other.

He said the woman was aged 21, but police were yet to confirm her identity.

A post-mortem was carried out in Auckland on Friday afternoon.

Det Snr Sgt Begbie appealed for anyone in the Tawera Road area overnight to come forward.

"Someone may have seen something unusual that has caught their eye or noticed suspicious activity around Tawera Road and Porowini Avenue. Any information could help us establish what may have happened before the woman was found in the stream." About 30 officers are working on the homicide investigation, and police still have a number of people to talk to, and several scenes to examine.