A boil water notice that was issued for several islands in Casco Bay, including Peaks, after a water main break on Little Diamond Island was lifted Thursday morning.

The Portland Water District issued a release saying tests showed the tap water was now safe to drink without first boiling it.

Michelle Clements, director of communications and public relations at the water district, said in an email that they still don’t know what caused the water line to break, but this time of year the district sees an increase in reports because of the cold and fluctuations in temperature.

“It’s a little more difficult to fix when it’s on the island because we have to work around tide schedules and get our material and equipment out there. It delays our response as far as fixing the break,” she said.

PWD began receiving reports at 6:15 a.m. Wednesday of low water pressure affecting Great Diamond, Little Diamond, Peaks and Cushing islands, said water district spokesperson Michelle Clements. By 9:30 a.m., crews had identified the water main break on Rockledge Avenue on Little Diamond.

A precautionary boil water notice was issued at noon for all of Peaks, Little Diamond, Great Diamond, House and Cushing islands. Consumers should boil water for 1 minute at a rolling boil before drinking, washing food, making ice cubes, brushing teeth or any other activity involving consumption, the notice said.

Jessica Grondin, spokesperson for the city of Portland, said crews from the Department of Public Works assisted the water district.

Staff Writer Grace Benninghoff contributed to this report.