Fairfax County, Va., fire investigators say improperly discarded smoking materials caused a massive construction fire that caused more than $48 million in damage at an incomplete mixed-use complex in Alexandria on February 8.

The fire, which investigators ruled as accidental, began in a second the second-floor trash chute of the project’s five-story residential building, which has been under construction for about one year. Construction workers evacuated the site after unsuccessful attempts to extinguish the blaze, which quickly spread to the top floor. Driven by high winds, the flames engulfed the project’s five main buildings and 14 townhouses, none of which had been fitted with sprinkler systems.

The fire also claimed a trailer, nearly 30 vehicles and multiple pieces of construction equipment. Several nearby occupied residences and apartment buildings sustained damaged as well. It took approximately 150 firefighters from four districts eight hours to bring the fire under control. During that time, the blaze’s heavy smoke appeared on National Weather Service radar scans.

Two firefighters and an unidentified “civilian” were treated for minor injuries and taken to local hospitals, according to Fairfax County Fire and Rescue.

The project, called South Alex, was scheduled to open in 2021 with 400 apartments, shops and a grocery store. Owner Combined Properties of Washington, D.C., has not disclosed the name of the contractor, but said in an online statement that it is “deeply committed to rebuilding and fulfilling our commitment to this neighborhood.”