Fire investigators do think the fire, in the 7100 block of 45th Street, was an accident. There were no reported injuries.
As a precaution, a third alarm was dispatched to assist putting the fire out, according to MCFRS spokesperson Beth Anne Nesselt.
Investigators said radiant heat from the initial fire impacted an adjacent house. A small fire could be seen on the roof of the house next door.
At the height of the fire, around 5 p.m. on Friday, there were more than 100 firefighters on scene.
Smoke from the fire could reportedly be seen in Rockville and throughout downtown Bethesda.
Photo via Maryland State Trooper Corey Green