An explosion at a chemical plant that manufactures fuel additives and solvents has rocked the Jacksonville, Fla., area, forcing evacuations and causing an estimated three deaths. The blast at T2 Labs — described by those at the scene as a “hellish inferno” and “a great ball of fire in the air” — also knocked out two of three generating units at an electric utility across the street, and left workers “shaken to the core,” said a local reporter.