PITTSBURGH (AP) — More than 100,000 Pennsylvania customers are being told to boil their water before using it.

At least two school districts canceled classes Tuesday after Pennsylvania American Water issued the advisory for parts of southern Allegheny and Washington counties.

The company advised residents to boil their water before using it for 48 hours. Sampling found high levels of turbidity, or cloudy water. The company says turbid water is harder to disinfect than clear water, increasing the chance of bacteria and other disease-causing organisms.