Witnesses said they heard an explosion and then saw flames shooting from the roof of a Gainesville transmission shop that caught fire Monday night.
"All of a sudden, it was just boom!" said Julian Novoa, who lives near the Trans Auto Dynamics transmission shop, just behind U.S. 29 in Gainesville. "It wasn't like an earthquake, but you could feel it."
Shortly thereafter, Novoa said he saw part of the long, white commercial building collapse as it burned.
Novoa was among about a dozen people who came out of their homes and cars Monday night to watch firefighters battle the blaze, which happened just after 7 p.m.
Prince William County Fire and Rescue units were called to the fire at 7:03 p.m.
Crews arrived on the scene to find the auto shop "heavily involved in fire leading to the roof collapsing," according to a post on the fire department's Facebook page.
Defensive operations kept the fire in check, the report said.
No injuries were reported. The cause of the fire is under investigation, the post said.
The transmission shop is located at 7510 Logos Way, near the intersection of U.S. 29 and Linton Hall Road. Fire crews battled the fire from Charis Avenue and U.S. 29.
Black smoke could be seen from U.S. 29 and from as far away as Bristow, said Del. Danica Roem, who had planned to go canvasing Monday night but ended up at the scene of the fire instead.
It's not clear what started the blaze or caused the apparent explosion. There was also no word yet about injuries or damage to the building.
"I saw this giant, black plume of smoke," said Roem, D-13th. "It was huge."
This is a developing story. Check with Prince William Times for updates.