The huge fire that broke out in Fairfax County on Saturday was caused by "improperly discarded smoking materials," officials said in an update Thursday.

Fourteen townhomes and five buildings were destroyed in the blaze that tore through a five-story building and filled the air with black smoke that could be seen for miles.

"The fire started in the second-floor trash chute of the residential portion of a multi-use complex. The cause of the fire was improperly discarded smoking materials," the Fairfax County fire department said Thursday morning.

It caused $48,171,075 in damage.

The fire broke out in a building that had been under construction in the 2800 block of Poag Street. One civilian and two firefighters suffered minor injuries.

A worker at the site first noticed the fire in a trash chute and called 911 at about 9:40 a.m. The worker tried to put the fire out but couldn't and escaped, firefighters said.

Firefighting units arrived within minutes of the 911 call but struggled to contain the blaze because of windy conditions and the building's lack of fireproofing.

Five buildings and 14 townhomes on the lot were considered a total loss.

In addition, 14 townhouses, four single-family homes, five apartment buildings, a commercial building and 28 vehicles were damaged.

The fire burned for hours. Ultimately, several other fire units were sent to the scene, including the City of Alexandria Fire Department, Arlington County Fire Department, Prince George’s County Fire and Emergency Services Department and Fort Belvoir Fire and Emergency Services.

Residents throughout Virginia and D.C. reported seeing black billowing smoke from the scene.

Firefighters said later Saturday that the fire was contained, but units stayed on the scene into the evening to put out hot spots and ensure the flames didn't kick back up.

Photos: Massive Fire in Fairfax County Destroys Building

Photos: 4-Alarm Fire in Alexandria Closes Route 1, Firefighters Say