A warning not to eat shellfish is in place for parts of Whangarei Harbour.
Northland District Health Board says heavy rain last weekend has caused stormwater to enter Whangarei's sewerage system, causing spills from pumping stations.
The affected area is upstream from Waikaraka and the warning applies for the next 28 days.
The DHB has also warned people to avoid contact with harbour water in the area during the next seven days.
It says people should follow sensible hygiene precautions if contact is unavoidable.