The Ruapehu District Council is warning people to avoid some local waterways which have become contaminated with sewage.
The council says it follows flood waters breaching the Raetihi and Ohakune waste water treatment plants.
Council chief executive and Civil Defence controller Peter Till said on Wednesday that people should avoid the Makotuku Stream and the Mangawhero River.
Mr Till said there are signs up warning people not to drink, swim, bathe or collect food from either waterway.
Water treatment in the area has stopped and residents should conserve water, he said.
Raetihi residents were already without tap water because of a diesel spill contaminating their supply.