An explosion rattled a North Bethesda townhouse early Thursday, with enough force to knock out a window and a door and attract the attention of nearby police officers.
Fire investigators consider the incident an arson, Montgomery County Fire & Rescue spokesman Pete Piringer said. He said investigators had not yet determined what caused the explosion, but it might have been a flammable liquid.
Montgomery County police officers on patrol in the area heard “some commotion, noise and an explosion” at about 2:15 a.m. and responded to a house on the 11000 block of Cedarwood Drive, Piringer said.
They found the main floor in flames and the front window and back door blown out.
The officers assisted a woman out of the house, and she was taken to a local hospital, Piringer said. She was being treated for injuries that he said were serious but not life threatening.
Another person escaped from the house and was not injured, he said.
About 45 firefighters arrived at the scene and quickly controlled the flames, he said. The fire caused about $40,000 to $50,000 in damage and displaced the two residents.
Montgomery County police said they could not provide further information as the fire department was handling the investigation. Piringer said no one has been charged.

The front window of the townhouse was blown out by the explosion. Via Pete Piringer/Twitter