(Washington, DC)  —  Federal investigators are moving against a massive sanitation company that’s accused of employing children as young as 13 on dangerous overnight shifts at food processing plants.  The Department of Labor requested a temporary injunction Wednesday against Wisconsin-based Packers Sanitation Services after investigators found at least 31 children employed to clean industrial equipment.  A Labor Department complaint said at least two child workers suffered caustic chemical burns and other injuries while working on the floor where cattle are butchered at a plant in Grand Island, Nebraska.  Investigators said they found child workers also at two plants in Minnesota.