STRATFORD, WI (WTAQ) - Police in the central Wisconsin village of Stratford are looking for the person who left a bomb threat in a bathroom at the middle and high school complex.

The building was evacuated around 1:40 p.m. Tuesday. Fire chief Bill Griesbach said it was about 20 minutes before the note said the school would blow up.

A nearby elementary school was also evacuated.

Police said X-rays in the area of the bomb threat turned up nothing. Teachers joined a regional bomb squad as they scoured through the classrooms and locker rooms – and they found nothing.

An all-clear was given around 3:45.

Stratford Police Chief Korey Schillinger said the school district did the appropriate thing by letting the youngsters leave. They were sent to a pair of church parking lots, where buses eventually took many students home. But those who drove to the high school had to wait until the all-clear was given.