A burglar alarm at the vacant Broad Street Elementary School in Butler ended with three youths in trouble with the law.

Butler police said they went to the school building around 3:25 p.m. for the burglar alarm. Officers found an open door and heard people inside the building.

There was no forced entry, however, police Capt. James Hollobaugh said Tuesday.

Moments later, police said, officers found and detained two juveniles outside the building.

The officers entered the building and searched it. They found a third juvenile hiding inside. He was taken into custody.

The three youths — all 15-year-old boys — were taken to the police station.

Police said they did not know what the boys were doing at the building other than running around.

Two of the juveniles were released to their guardians. The other boy was detained by Butler County Juvenile probation authorities. He was already on juvenile probation, Hollobaugh said.

That same boy was subsequently placed at the Keystone Adolescent Center in Greenville, Mercer County.

All three teens are charged with criminal trespass in Butler County juvenile court.

Broad Street Elementary School was closed in 2015 as part of the Butler School District's consolidation plan.

It was put back into service in 2017 as a temporary home for teachers and students from Summit Township Elementary School, while Summit was being connected to a public water line after water quality tests raised concerns about the amount of lead and copper in the water supply.

No damage was reported at the school stemming from Monday's incident.