Engineers are testing the water at Center Township Elementary School after a teacher on Monday discovered “black particles.”

Teachers and students have stopped using the water fountains in the school until Gannett Fleming engineers can test samples and determine what the particles are, according to a letter sent home to parents by Principal Jeffrey Mathieson. Use of drinking water at the school won’t resume until tests show that it is safe.

The issue may have started after the school experienced a power outage last Thursday.

“This power outage had a negative impact on our water pumps, causing a significant reduction in water pressure. The maintenance department is working to rectify that issue with the water pumps as well,” Mathieson’s letter reads, in part.