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.

The haze and chemical smell had spread to Atlanta by Monday morning, prompting firefighters to use detectors to check the quality of air in various parts of the city, Mayor Andre Dickens said. Closer to the source of the fire, officials said chlorine, a harmful irritant, had been detected in the air from the fire at the BioLab plant in Conyers, Georgia, the Rockdale County government said in statement early Monday. The plant is about 25 miles (40 kilometers) southeast of downtown Atlanta.