Glassboro police said they became aware of a possible threat to an unnamed school that was posted on social media.
All schools in the district were put in a shelter-in-place out of an abundance of caution as authorities investigated the credibility and origin of the threat, police said.
Chopper 6 showed police vehicles outside Glassboro High School on the 500 block of Joseph Bowe Boulevard.
Police respond to Glassboro High School, investigation underway
Police later determined the threat originated from another state and there was "no credible danger" to the schools.
The shelter-in-place was lifted around noon.
The department said officers will remain outside each of the schools for the remainder of the day as a precautionary measure.
The criminal investigation is continuing with the assistance of the Gloucester County Prosecutor's Office and additional agencies.