Emergency dispatchers said the substance was found late Monday morning in a bottle on the playground outside the Pine Forge Elementary School on Glendale Road in Douglass Township, Berks County.
Officials at the school, which is part of the Boyertown Area School District, said the materials appeared to be the result of vandalism over the weekend.
Police and firefighters responded to the scene. They requested the response of the Reading Police Department Bomb Squad to check out the materials.
The bomb squad couldn't determine exactly what the materials were, so it removed them for testing.
While all that was going on, students were relocated away from the area to other parts of the building as a precaution.
Information from WFMZ-TV