Swimmers are being advised to steer clear of the Raglan Harbour following a sewage overflow last week.

Waikato District Council advised the public not to swim, fish or collect seafood.

It is estimated that about 10 cubic metres of wastewater entered Raglan Harbour at high tide on Friday.

Council general manager service delivery Tim Harty said staff are sampling the water every day and working with Waikato District Health Board and Waikato Regional Council to determine when the advisory notice on the harbour can be removed.

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"It can take about five days to receive test results from the sampling, so it is possible signs may be removed by the weekend," he said.