The building was not evacuated. Some streets in the area were temporarily blocked during the investigation.
Shortly before 8 p.m., investigators identified the powder as sodium azide, according to Sgt. Cortez Stafford with the fire department. The salt is a common component in vehicle airbags.
According to the Atlanta-based Centers for Disease Control and Prevention, it is a potentially deadly chemical that can quickly change into a toxic gas. In airbags, an electrical charge triggered by a crash causes sodium azide to explode and convert to nitrogen gas inside the airbag.
The investigation into the incident continued late Thursday.