Helicopters, including the Police Eagle helicopter, are continuing to search Kaipara Harbour after a boat got into difficulty.
Emergency services have been told that 11 people were on the vessel.
Although at this stage Police are unable to confirm figures, there are a number of fatalities.
A number of people have been rescued.
Police are also working to establish who was onboard the boat.
As the operation is ongoing, information is subject to change.
The rescue operation continues this evening and is fully resourced, with the assistance of the Coastguard, St John, Surf Life Saving and Victim Support.
Anyone who has concerns about the welfare of relatives in relation to this incident is asked to attend Helensville Police Station or call 111 for assistance.
Police continue to appeal to boaties and pilots to steer clear of the Kaipara Harbour area while the rescue operation is conducted.
Emergency services require a safe working space around South Head.
The Police Media Centre will release more details this evening.
ENDS
Police Media Centre