Untreated wastewater has leaked into the sea at Wellington's south coast due to a treatment plant equipment failure.
About 5000 cubic metres of wastewater - enough to fill two Olympic-size swimming pools - was discharged from the Moa Point Wasterwater Treatment Plant for about two hours last night.
The discharge occurred at the short outfall pipe near the dog pound from about 8.30pm.
Regional public health officals have been informed, and warning signs have been put up in Tarakena Bay and Heu Te Take Peninsula.
The beach at Lyall Bay was not affected.
Water quality testing of near the discharge site is under way and will continue for three days.