A massive explosion at a chemical plant in Georgia caused a huge plume of smoke, and authorities have instructed residents and businesses to shelter in place.

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.”

For everyone sheltering in place, the best practice is to turn the air conditioning off and keep windows and doors shut,” a statement said.