Swimmers are being warned to stay out of the water at popular Auckland beaches after a raw-sewage spill caused by Tuesday's power failure.
And the city council is worried contamination could spoil Waitangi Day events.
The power outage affected the Orakei wastewater pumping station and meant sewage spilled into the Waitemata Harbour.
Auckland City's environmental health team has posted signs at Okahu Bay and Mission Bay advising of the poor water quality. Signs were also added to Kohimarama and St Heliers beaches yesterday "as a precautionary measure", because the council was concerned the wind and tide would spread the wastewater further along the coastline.
The beach closures coincide with the Louis Vuitton Pacific Series, based in the Waitemata Harbour, and precede the Waitangi Day Festival.
"It is very unhelpful at a time when we are trying to showcase Auckland to the world ... We do feel let down by Transpower," said the council's chairman of city development, Aaron Bhatnagar.
He said the Louis Vuitton regatta was largely unaffected by the spill because its tourism centre was in the Viaduct Harbour.
Team New Zealand boss Grant Dalton confirmed last night that the spillage had not troubled the yachting series.
"The racing is further out in the harbour, and we are too busy sailing to notice this sort of thing. It is business as usual for us."
But the council is concerned about the effect on Waitangi Day events including traditional sailing yachts, waka, and a re-enactment of Governor William Hobson's 1841 landing at Okahu Bay.
Council spokeswoman Angelika Doughty said results from water-quality testing were expected this afternoon.
Watercare has installed emergency generators at the Orakei pumpstation to ensure it can continue operating during rolling power outages.
Auckland Regional Public Health Service spokeswoman Sally Young said it was usual to prevent swimming in a wastewater overflow. "It is best to take the safe way and ask people not to swim or collect shellfish for 48 hours after a spill."