Smithfield, N.C. — Smithfield has been placed under an advisory ordering residents to boil water, because testing of water samples detected the presence of coliform bacteria, officials said.

Coliform bacteria aren't dangerous, but are an indicator that other, potentially harmful bacteria might be present.

Residents should boil all water used for human consumption, such as drinking, cooking, brushing teeth, making ice and washing hands. Boiling water for at least one minute should kill the bacteria.

Spokesman Lu Hickey said that the Johnston County Public Utilities Department stopped buying water from Smithfield after the advisory was issued, so county retail and bulk customers are not affected. An advisory is not in effect for the Glad Acres and Maple Wood Run subdivisions, Hickey said.