Federal officials are investigating what led to the fire and how it has been handled. The sprinkler system showered water onto water-reactive chemicals around 5 a.m. Sunday, Rockdale County Fire Chief Marian McDaniel said. There were employees inside the plant, but no injuries were reported.

Atlanta’s fire department said it was testing for the presence of chemicals including chlorine, hydrogen sulfide, and carbon monoxide. Residents east of Atlanta were again warned Tuesday to take shelter where they are if shifting winds push the still-billowing chemical cloud from a chlorine factory fire over their neighborhood.