People have been advised not to swim in the Wairoa River after high levels of E.coli were detected.

The results prompted the Hawke's Bay District Health Board to ask the Wairoa District Council to erect warning signs recommending people not swim in the river until further notice.

The DHB said the elevated Ecoli levels could have been caused by a number of factors, including contaminated run-off from farmland, birds, or other sources, and noted the situation followed recent rain events over the past two weeks.

The warning followed another issued last month for the Nuhaka River, near Mahia, where extremely high levels of fecal matter, 20 times higher than safe swimming guidelines, had been found.

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In that case, the DHB said the readings were not related to rainfall, rather it was suspected the river mouth may have got blocked up meaning the bugs were unable to disperse down the river.

On the Land Air Water Aotearoa (LAWA) website, it was noted there were a number of discharges into the Wairoa River, including downstream discharges from Affco Wairoa and the municipal sewage discharge.

Additionally, there were a number of stormwater drains which flowed into the river, and both active and closed landfills near the mouth of the river. Elevated bacteria levels, however, were generally seen after heavy and prolonged rainfall.

The LAWA website contains regularly updated information about the safety of swimming spots at beaches, rivers and lakes.

As of yesterday, caution warnings were in place for Puhokio Stream at Waimarama Beach and the Tukituki River at Black Bridge, Haumoana.

While not as serious as the warning for the Wairoa River, and generally considered suitable for swimming, the cautionary status noted that younger children and older people may be at increased risk at times.

The Hawke's Bay Regional Council planned to carry out further tests at Wairoa River this week to see if the levels had reduced.

If people did swim in the Wairoa River and develop diarrhoea and/or vomiting between one to two days afterwards they were advised to contact the on-call health protection officer at the Hawke's Bay District Health Board, phone (06) 834-1815.