People are being warned not to swim in Waimarama's Puhokio Stream because of contamination.
Hawke's Bay District Health Board's medical officer of health, Dr Nicholas Jones, said monitoring by Hawke's Bay Regional Council had identified high levels of E. coli in water samples taken on December 12 and 14.
The levels exceed the maximum values recommended in the Recreational Water Guidelines and indicate that, at the time of sampling, there were excessive amounts of faecal matter, either animal or human, in the water.
"The stream has previously been given a grade of very poor suitability for swimming and the recent very high levels of contamination are a reminder to avoid swimming or playing in this water," said Dr Jones.
"It is easy to see how parents might think the stream is a safer option for young children, but, unfortunately, there is a risk of children getting sick.