HURST, Texas (CBSDFW.COM) – Authorities are investigating threats made via text message against students and staff at L.D. Bell High School in Hurst, police say.

District officials say administrators were made aware of the messages sent to 15 students and staff that threatened school safety.

Officers were called to the school to conduct a sweep of the building and to investigate. They have not yet determined who sent the messages. The contents of the message have also not been released.

The district says officers will remain on the campus for the rest of the school day Wednesday as a precaution as authorities continue to investigate.