Canterbury District Health Board is warning people to avoid fishing in the lower reaches of the Waimakariri River as sewage has been discharged into the waterways.
The DHB says with last week's heavy snow melting, and because of the fragile state of the earthquake-hit infrastructure, sewage has been discharged at Kaiapoi and Pines Beach.
The board is advising people to avoid contact with the water, and warns against any white-baiting or recreational use of the river.
This is in addition to the existing warnings which have been in place in other quake-affected areas of Canterbury, including the Avon and Heathcote rivers and estuary.