Inhabitants of Winnipeg, Canada's sixth largest city, have been warned not to use tap water without first boiling it, after E. coli bacteria was detected in the water supply, officials said Wednesday.

"In terms of the city of Winnipeg, this is the first boil advisory for the entire city of Winnipeg," said Geoff Patton, director of the city's water and waste agency.

The city's 700,000 resident were warned to boil before drinking it, using it to prepare food or brushing their teeth.

Residents also were urged to help toddlers or the elderly bathe to keep water from getting into their mouths.

No infections have been reported at city hospitals since the E. coli bacteria was detected in the water supply on Monday.

Symptoms include stomach pains and generalized vomiting.

The city said it issued the boil water advisory as a precaution after what it said were "atypical test results" showing E. coli in six of 39 samples of water, despite chlorine levels that surpassed requirements.

Officials were waiting for the results of a retest before deciding whether to lift the advisory.