A health warning for the Waimakariri River after consecutive samples found high levels of faecal matter

The warning affects the river upstream of the Old Highway Bridge North Bank.

Health New Zealand says rainfall in the area in the last few days has most likely caused the high levels of bacteria.

Spokesperson Dr Cheryl Brunton, says a number of other popular swimming sites in Canterbury may also be affected after recent rainfall.

Dr Brunton says the water may contain a range of disease-causing micro-organisms, which can cause more serious diseases like Hepatitis A or salmonella infection.