An estimated 350 properties are affected.
The presence of E. coli in the water supply was only confirmed by the laboratory this morning after water samples were taken yesterday.
"We've informed the Canterbury District Health Board of the discovery and are working with them to get the word out to homes, schools, businesses, childcare and healthcare facilities in the affected area," Mackie said.
The boil water notice would remain in place until laboratory tests confirmed the water was safe to drink.
Dr Ramon Pink, Canterbury Medical Officer of Health, said it was important residents in the Governors Bay area boiled or treated all tap water before drinking, brushing teeth or using it in food preparation.
"Bringing water to the boil is sufficient to kill bugs. If you cannot boil water, treat it by adding 1 teaspoon of household bleach per 10 litres of water and leave for 30 minutes," Pink said.
"The Christchurch City Council and Canterbury DHB's Community Public Health are working together to test water supplies in Governors Bay and will update this advice as soon as we have a clear idea of how the water supply has been impacted."
Pink said contaminated water could cause gastroenteritis.
"Gastroenteritis is usually self-limiting, and will settle within one to two days. Dehydration is the main concern and so drinking plenty of fluid is important. Most people will not need to see a doctor but if your symptoms persist, or you are concerned, call your GP team for advice."