PAPILLION, Neb. (AP) — Authorities say they’re investigating an anonymous bomb threat against a Papillion high school that was posted online.

The Papillion-La Vista School District says it discovered the threat against Papillion-La Vista South High School on Twitter Sunday afternoon. Papillion police searched the school Sunday night and Monday morning and found nothing. There were extra officers at the school Monday.

District officials alerted parents and students about the threat Monday. Some students left the school early in response.

District spokeswoman Annette Eyman says the Twitter account posted three threatening tweets against the school. The account is no longer accessible online.