A health warning is in place for the Makino Stream and Oroua River near Feilding, after authorities were alerted to a significant discharge of effluent.
Horizons Regional Council were alerted to the issue over the weekend and after seeking advice from public heath, have issued a warning for these waterways.
HRC strategy and regulation group manager Dr Nic Peet said they were particularly concerned for anyone using the Makino Stream or Oroua River, downstream of Rata St.
"This includes wading, swimming at popular spots such as Awahuri and Kopane, fishing, and gathering watercress. Public Health asks that anyone who has been in the water in these areas and have produced gastro like symptoms to get in touch with their GP or ring Healthline on 0800 611 116."
Three Horizons pollution response officers identified the animal effluent on Friday evening and ordered it cease immediately.