At 8:40 am school was dismissed at East Pennsboro High School.
A spokes person for the school district says a written bomb threat was discovered in a bathroom inside the high school building.
When asked why the school was closed instead of a temporary evacuation CBS 21 news was told administrators thought it would be easier for police to do their investigation.
Detectives at the East Pennsboro Township police department are using surveillance video from a camera located outside the bathroom where the threat was found as part of their investigation.
Classes and activities will resume as normal tomorrow morning.