ATLANTA — Federal authorities have released an update on the investigation into fires at the BioLab chemical plant near Atlanta. The September blazes produced a toxic chemical cloud that forced nearby residents to shelter in place. Fires at the BioLab plant in Conyers, Georgia, sent a huge plume of orange and black smoke into the sky. The U.S. Chemical Safety and Hazard Investigation Board on Friday released an investigation update. The report lays out a timeline of events, beginning when an employee heard a "popping sound" around 5 a.m. and tried unsuccessfully to isolate the reacting product.