Police presence greeted Artie Henry Middle School students Tuesday morning after a threat was found on a girls' bathroom wall.

According to a letter from the Cedar Park school's officials, graffiti found in the 6th grade girls' bathroom last week said, "I'm going to blow up the school on May 13th."

The graffiti was cleaned up and Cedar Park police investigated.

Bomb sniffing dogs searched the campus as a precaution but nothing was found.

Principal David Ellis said he believes a 6th grade girl is behind the graffiti, but no suspect was identified.

A letter was sent home to parents.