A 17-year-old girl is in police custody in connection with an online threat against schools in the Chester Upland and Chichester School Districts.
Investigators say the teen was taken into custody at a sleepover.
The FBI is involved in the investigation.
A message was posted on Instagram Tuesday night threatening black students at schools in the Chester Upland School District, Chester Community Charter School and Chichester High School. Another message threatened students at "Lincoln," but did not specify which school with that name it was referring to.
Chester Police and the FBI are both investigating, but have not yet revealed whether the threat is valid.
“The department has enlisted the help of the FBI and combined resources from neighboring towns,” said Chester Police Commissioner Darren Alston.
Chichester School District Superintendent Dr. Kathy Sherman also released a statement on the threat on the district Facebook page.
Breaking news and the stories that matter to your neighborhood.
“An instagram message was circulated on social media this evening. Police and Authorities were notified immediately and are working to determine its credibility,” she wrote. “At this time, we do not have any further information. Due to the late time, we will update you via the Alert system in the morning. Please know that the safety of our students and staff is our main priority.”
Officials have not yet revealed what specific actions they are taking, but say the investigation is ongoing.