(Radio Iowa) – The U.S. Labor Department says a Tennesse-based cleaning company will pay $649,000 in penalties for employing children at facilities that included the Sioux City Seaboard-Triumph pork plant.

An investigation earlier this year found that children, some as young as 13, were put on overnight sanitation shifts at the Sioux City plant and Perdue farms facility in Virginia. At the Seaboard Triumph facility, federal investigators witnessed children concealing their faces carrying glittered school backpacks before starting their overnight shift.

They learned children were assigned to use corrosive cleaners to clean dangerous kill floor equipment. Seaboard Triumph has since fired the company.