Students at the Peoria, Illinois, District 150 schools became ill after eating lunches with flour tortillas. The first episode of illnesses occurred in December, 2005, when about 80 students at five schools became ill. In January, 2006, an additional 150 students became ill. The same tortillas were served in the lunches preceeding each outbreak. The tortillas were found to contain an usual amount of a preservative (not specified).