Swimmers are being told to steer clear of the water at popular beaches on the North Shore.
Auckland Council has put up warning signs at Takapuna after water quality tests returned poor results.
The tests record levels of specific bacteria that could be a risk to human health, the council said.
Neighbouring beaches Milford, Mairangi Bay and Long Bay have had inconclusive test results and require further testing to confirm whether there was a serious risk to health.
The council would be in a position to advise on any further action later this afternoon when the results are in.
Auckland Council would be investigating to confirm the source of contamination.
Earlier this week similar signs went up at Clarks Beach and at Laingholm Beach but tests since have shown good results.
NZME.
