A 'modified lockdown' at Edmond Memorial High School was lifted Wednesday after authorities determined a threat they investigated was not credible.

Police said the threatening message was written on a wall in a boys' bathroom. 

Extra officers were added to patrol the campus and completed an investigation into the non-specific threat.

A modified lockdown happens when all exterior doors and classroom doors are locked, however classes continue as normal. Modified lockdowns are put in place when there is no immediate threat at the school.