Loudoun County house explosion kills 1 firefighter, injures 9 more and 2 civilians: fire officials

STERLING, Va. -- A house explosion in Sterling, Virginia killed 1 firefighter and injured 11 more people, a mix of firefighters and civilians, Friday evening, Loudoun County County fire officials said.

Loudoun County Fire and Rescue Assistant Chief of Operations James Williams said that firefighters responded to a home on Silver Ridge Place in Sterling on Friday evening. After their arrival, while they were conducting an investigation, the house exploded with firefighters inside.

One of those firefighters was killed, and nine more were injured, Williams said. Some of the firefighters sustained serious injuries. Two civilians were also injured.

The Sterling Volunteer Fire Company tweeted that firefighters had been dispatched to that home for a reported gas leak, but Williams would not confirm that information, saying the cause of the fire was still under investigation.

The debris field is large, stretching into the street and into the vicinity of neighboring homes. The house that exploded is completely destroyed and the fire from the explosion continues to smolder, according to the assistant chief.

"This is the worst call that we can respond to," Williams said.

The ATF and the Loudoun County Sheriff's Office are assisting in the investigation, Williams said.

ABC News contributed to this report