School officials say the note was found on a bathroom door by a student and upon the discovery, police were immediately notified.
Officers with the Warminster Township Police Department used specially trained K-9 dogs to inspect the entire building and the grounds surrounding the school.
Around midnight, the area was found clear of hazards and deemed safe.
At the request of school officials, there was an extra police presence Friday morning as students arrived.
Students were required to enter through a single entrance and their bags were subject to a thorough search as a precautionary measure.
During the school day, no problems were reported.
Police now believe that the note was a hoax but the incident remains under investigation.
Anyone with information is asked to contact the Warminster Township Police Department at 215-672-1000 or 215-443-5000.
