A Lakeville, Minnesota, school reported that a significant portion of their students were absent due to illness on May 4. Over 20% of the school was ill prompting an investigation by the state health department. Epidemiologists conducted interviews with students and staff to identify cases and gather food histories. A total of 29 cases were identified, with twelve more students suffering from more mild gastrointestinal illnesses. Analysis of the food histories proved to be rather complicated due to probable secondary cases. The initial analysis included secondary cases and found multiple foods associated with illness. Subsequent analysis removed the secondary cases; this analysis found a significant risk associated with the consumption of cookie dough. A traceback of the cookie dough was conducted and it was found to be a commercially produced item that used pasteurized eggs. However, a warning label stated "this product should not be eaten raw." Stool samples were collected from three students. Two of these tested positive for Norovirus and one for Campylobacter jejuni. The health department concluded that Norovirus was more likely the cause of the oubreak due to the symptoms of most students and that the C. jejuni infection was coincidental. They also concluded that the outbreak was due to contamination of the cookie dough at the school either by ill volunteer food workers or the children sharing food.