The Boston Fire Department has determined the cause of the massive fire that tore through a condominium complex in Charlestown on July 21.
According to the department, the most likely cause of the 6-alarm fire was careless disposal of smoking material.
There was no propane grill in the building.
No one was injured in the fire, however, one firefighter was transported to the hospital for heat exhausion.
The fire caused millions of dollars of damages.