Minnesota health workers noticed a cluster of Salmonella Heidelberg isolates that matched each other genetically. This cluster initiated an investigation which began with analysis of the food histories of the case-patients. Recent consumption of frozen, stuffed chicken meals was commonly described by the case-patients. A case-control study found this association to be statistically significant. The Minnesota Department of Agriculture performed a traceback and found the chicken meals all came from Cub Grocery stores. The meals were traced to a line of products produced at a plant in Illinois. The chicken meals were pre-browned but not cooked, and at least two of the case-patients indicated they had not read the cooking directions properly. The "broccoli and cheese" stuffed chicken, and the Chicken Kiev were indicated by the case-control study and food histories. A Michigan case indicated another variety of stuffed chicken, Chicken Cordon Bleu. Salmonella Heidelburg was isolated from product samples. After being notified of the outbreak, the Cub Grocery Stores voluntarily pulled the entrees from their shelves, and redesigned the labels to prominently display cooking directions.