Health warning signs have been posted in Tauranga harbour and estuaries after an overflow of wastewater caused by torrential rain on Tuesday.
The flooding damaged culverts and pipes in Otumoetai and wastewater flowed into the Waikareao Estuary.
Swimmers are being advised to stay out of contact with water in the inner harbour and estuaries.
The warning extends to Pilot Bay in Mount Maunganui and Welcome Bay further inland, at a time of year when many locals would normally use the water for triathlon training.
People are also advised against gathering seafood until at least Thursday, when an update on test results will be issued.
Tauranga City Council says some warning signs are likely to be in place for a week. However drinking water supplies are fine.
Heavy rainfall on Tuesday damaged culverts, pipes and roading and also caused large slips around the Mount base track.
With extra generators, Tauranga's Chapel Street treatment plant processed 36,000 cubic metres of water, compared with its normal maximum capacity of 20,000 cubic metres.