A modular building at Highland Park Middle School in Beaverton was destroyed by fire Tuesday morning.
The building was fully involved when crews arrived. They had difficulty accessing the building, because of a fence. Once they got water onto the structure they quickly knocked down the flames.
Power lines had burned through and were on the ground posing a hazard to firefighters.
The modular building is separate from the main school building which was not damaged.
Investigators are working to determine how the fire started.