Pennsbury School District was closed Friday as a boil-water advisory remained in effect for Yardley, Lower Makefield, and Falls Township.

On Thursday night, a water utility had told residents to boil tap water before consuming it due to the potential presence of disease-causing organisms.

Pennsylvania American Water said in a statement on its website that it was investigating "high turbidity levels" in the water being supplied to those parts of central and lower Bucks County. It advised residents to boil water before drinking it, making ice, brushing teeth, washing dishes, or using it to cook.

It did not say when it might be safe to consume tap water again, but said it would alert residents at that time. As of Friday morning, there were no additional updates from the water company.

As a result, Pennsbury School District, which serves about 10,000 students, said all of its 15 schools and its central offices would be closed Friday and that it would continue to monitor the situation through the weekend.

The utility said the spike in turbidity levels, which it deemed temporary, was caused by "changes in water flows to filters at our treatment plant."

It did not elaborate and said an investigation was ongoing to determine a solution. Turbidity — or cloudiness — may indicate the presence of bacteria, viruses, or parasites that can cause nausea, diarrhea, or headaches, the utility said.

Tankers with potable water would be stationed at the Yardley Makefield Fire Companies; Big Oak Shopping Center; Village Market in Lower Makefield; and Gas Light Village in Falls Township, according to the utility.

Yardely borough advised residents that Brita or other water filters were not adequate in this situation, that pets should be given the same boiled or bottled water as humans, and that showering was OK.