In late July, 2006, three E. coli O157:H7 cases were reported to public health agencies. Their isolates were a genetic match to one another. These people were residents and visitors of Longville, Minnesota. At the same time, an outbreak of E. coli O157:H7 was reported among members of the Salem Lutheran Church of Longville. The church served a meal on July 19 which appear to be a risk factor for illness. Consumption of potato salad, hamburger, and ground beef were associated with risk of illness. Ground beef was used to make meatballs for the meal. The ground beef had been purchased from Tabaka's Supervalu. The Supervalu obtained beef chuck rolls from Interstate Meat on July 10. Most of this chuck was ground into hamburger meat. A traceback of the Interstate Meat showed that it originated from a Nebraska Beef processing plant. Beef trimmings collected at Nebraska Beef on June 14, cultured positive for the outbreak strain of E. coli O157:H7.