Residents in some areas of Whangarei are being warned not to drink or use discoloured tap water.
Fresh water in the One Tree Point area has been discoloured because of an unusual surge in water use in Bream Bay's industrial area.
Sediment in the pipes has been disturbed and mixed with the water causing it to turn brown.
The council says residents should not use the water for drinking, cooking or washing and should call the council on (09) 430 4200 if they need fresh water delivered.
Council contractors are flushing the pipes to fix the problem.