The Henry School in Philadelphia was temporarily evacuated Tuesday afternoon, and 15 students and five adults were treated for exposure to pepper spray, school district spokeswoman Shana Kemp said.
Philadelphia police are investigating how the spray was released in the school just outside the cafeteria about 12:50 p.m., as students were leaving lunch.
"We're not sure if it was a student or an adult. We think it could have been a student," Kemp said.
It was the second time that day that pepper spray was released at the school at 601 Carpenter Lane in West Mount Airy. The first occurred in a hallway about 9:30 a.m., and five students were affected, Kemp said.