A  flash fire broke out at George C. Marshall High School in Falls Church Saturday morning and resulted in an estimated $20,000 worth of damage, Fairfax County Fire and Rescue officials reported today.

Fairfax County Fire and Rescue Department units responded to the fire at the school located at 7731 Leesburg Pike at approximately 10:25 a.m. on May 18 where firefighters reported smoke coming from the school upon arrival. Firefighters conducted an aggressive fire attack and brought the fire under control in approximately 10 minutes, officials reported.

Five individuals working in the school were treated at the scene. Officials say fire alarms were activated, but because it was only a flash fire, sprinklers did not activate

According to fire investigators the cause is undetermined.

Damage is estimated at $20,000. School will open Monday on schedule.