Authorities placed Brownsville’s Porter High School under lockdown after four unknown men entered campus without permission.

It all happened around between 3 and 4 p.m. Thursday.

Brownsville ISD officials said the four men were not students and entered the rear of the campus without permission.

Investigators arrested two of the four men at the scene and charged them with criminal trespassing.

The other two men escaped but are being identified by law enforcement officials searching the area.

Brownsville ISD officials said the high school was only under lockdown for one hour.