Units were called to 13820 Sunrise Valley Dr. in Herndon, near the Westin Washington Dulles, about 7:45 p.m.
Firefighters said they encountered heavy smoke coming from the lower level of the 10-story building upon arrival. Upon further investigation, firefighters found fire in the first floor “battery room.” Additionally, an outside transformer caught fire near the building.
The incident commander issues a second alarm, which brought more than 60 firefighters to the scene.
There were approximately 50 employees in the building when the fire broke out. All were able to get out of the building. There were no injuries.
Firefighters were able to contain the fire to the room of origin and transformer with no fire extension to other parts of the building.
Firefighters said the automatic fire alarm did activate; however, a security officer called 911 after hearing an explosion. One sprinkler head did activate helping to keep the fire contained.
Damage is estimated at $2 million.
The fire has been ruled accidental. An electrical event in the control module to the uninterruptible power supply caused the fire, officials said.