The East Pennsboro Area (Pa.) School District has closed all four of its schools while workers test the facilities for mold contamination.

The district, based in Enola, Pa., closed all its schools Wednesday and says they will remain closed while district officials conduct air quality tests.

The schools affected: East Pennsboro Elementary, West Creek Hills Elementary, East Pennsboro Middle and East Pennsboro High.

Mold was discovered Tuesday at East Pennsboro High and Elementary, and students at those two campuses were sent home early. District officials subsequently decided to conduct environmental tests at those campuses as well as East Pennsboro's other two schools. Classes throughout the district were canceled.

"The district will be conducting additional testing and inspections of the heating and cooling systems of each building," the district stated in a message to patrons. "This is a precautionary measure to ensure the safety of all students and staff."

Administrators had expressed optimism that the two elementary schools and the middle school will be able to reopen on Friday, but the discovery of mold at East Pennsboro Area Middle and West Creek Hills Elementary prompted the additional cancellations.

The high school will be closed at least through Monday as cleaning takes place there.