A chemical cloud formed in a plant early Monday morning after an accident in a mixing room, exposing more than 90 workers and firefighters to toxic fumes, authorities said.

The Anchor Hocking Packaging Co. plant was evacuated when the accident occurred shortly before 3 a.m., said Fire Capt. Robert Rathi.Thirty-four plant workers were treated at Frick Community Health Center for symptoms including headaches, burning of the throat and nose and nausea, said spokeswoman Jeanne Toohey.