Meatpackers and other companies in the food-supply chain need to do a better job taking steps to ensure illegal child labor isn’t being used in their operations, or by their suppliers, subcontractors or other vendors.

That’s according to US Agriculture Secretary Tom Vilsack.

In a letter to 18 of the country’s largest meat and poultry companies, Vilsack advised the packing industry to take more actions to ensure their supply chains are not using illegal child labor.

The letter comes after a food sanitation company, Packers Sanitation Services Inc., was fined $1.5 million in February following a Department of Labor investigation that found at least 102 children from ages 13-17 years old were working in hazardous occupations, often on overnight shifts, in at least 13 meat processing facilities across eight states.