Pottsgrove Middle School was evacuated Thursday morning because several students were hospitalized after passing out, but investigators found no environmental hazard in the building.

The Pottsgrove School District said three students fainted during a choral practice. As medical responders were treating those students, others reported that they felt light-headed or dizzy.

In total, 22 students were taken to Pottstown and Phoenixville hospitals for evaluation. But the school district said emergency crews found no apparent environmental hazard in the building and no cause for most of the students' symptoms.

"It was panic that ensued, seeing the other kids who were sick," superintendent Shellie A. Feola said. She said the students had been released from the hospitals and were doing fine. - Emily Babay and Jessica Parks