A small fire on the plant’s roof was initially contained but reignited Sunday afternoon, authorities said. More than 90,000 residents east of Atlanta were told to keep sheltering in place Monday a day after a chemical plant fire sent a massive plume of dark smoke high into the sky that could been seen for miles.

Rockdale County officials ordered people to evacuate the area near the BioLab plant in Conyers, Ga., and they said others should stay home to avoid the “harmful irritant chlorine.”