The fire ignited when a sprinkler head malfunctioned around 5 a.m. Sunday at the BioLab plant in Conyers, Rockdale County Fire Chief Marian McDaniel told reporters. The malfunction caused water to mix with a water-reactive chemical, producing a plume of chemicals.

County officials said that around 5 a.m., a sprinkler head malfunctioned, causing a mixture with a "water-reactive chemical," which in turn started a small fire on the building's roof. That fire was contained and put out, but reignited around noon. The fire was again put out around 3:30 in the afternoon.