A water main break has led the Portland Water District to issue a boil-water order for residents of Peaks and Cushing islands in Casco Bay.

The order took effect 9:30 a.m. Friday, and applies to any water that residents intend to consume, the city said in an emergency message to residents.

Water should be brought to a rolling boil for at least one minute before it is used to wash food, make ice cubes, brush teeth or otherwise be consumed.

The Portland Water District reported Friday afternoon that the leak affecting Peaks Island had been isolated and water pressure restored, but the boil-water order would remain in effect.

Water samples will be collected and tested within the next 24 hours. Updates about the boil-water order will be shared on Facebook and the water district’s website, district officials said.