One firefighter was killed — and at least nine other firefighters and two civilians injured — in a massive home explosion in Northern Virginia’s Loudoun County Friday night, officials said.

In a news briefing, Loudoun County Fire and Rescue Assistant Chief of Operations James Williams said that fire crews were first called to the home in the community of Sterling at about 7:40 p.m. local time.

“Soon after arrival, with firefighters inside, the house did explode,” Williams said.

One firefighter was killed in the explosion, the assistant chief disclosed. The victim’s name was not released. Nine other firefighters and two civilians were rushed to area hospitals.

“The nine firefighters have some serious injuries, as well as some less severe injuries,” Williams said.

Aerial footage from CBS affiliate WUSA-TV showed widespread debris from the explosion, with heavy flames burning and smoke billowing hundreds of feet into the air. 

“Total devastation, there’s a debris field well into the street and into neighboring homes,” said Williams, but he could not immediately confirm the extent of the damage to surrounding properties.   

Williams said all firefighters were now “out of the building,” adding that the “fire will continue to smolder for an undetermined amount of time.”    

The circumstances leading up to the explosion were unclear, and Williams wouldn’t speculate on the cause, only saying that it was under investigation. However, the Sterling Volunteer Fire Company had reported on social media that it had responded to a gas leak at the same address a little before 7:40 p.m. 

Local utility provider Washington Gas said in a statement to CBS News that it was “verifying the integrity of our system in the surrounding area.”

Sterling is located about 25 miles northwest of Washington, D.C.