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.
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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.