E-coli has been found in the water supply in the South Taranaki town of Waverley.
"Routine tests have detected the bacteria Escherichia coli in the Waverley Water Supply, and investigations are now underway to find the source," South Taranaki District Council says in a statement.
The Council says the bacteria was picked up during routine testing.
"Residents are advised to boil all water used for drinking, brushing teeth or for food preparation until further notice," it adds.
"Anyone showing symptoms of sickness should visit their doctor as soon as possible."
Investigations are underway to find the source, but the council says testing has indicated the water bores are clear of the bacteria.