The Minnesota Department of Health foodborne illness hotline recieved a call on February 10 regarding three ill people who had all dined at a prime rib restaurant in Fergus Falls, Minnesota. A second report came in three days later. Epidemiologists began calling recent patrons of the restaurant to see the number of ill people and the common exposures. Stool samples from the two callers revealed the cause of the illnesses to be Clostridium perfringens. The phone survey found twenty-five people fitting the case definition of having vomiting or diarrhea after eating at the restaurant. Those who had eaten the prime rib were fifteen times more likely to become ill; this was the only statistically significant exposure. An environmental investigation of the restaurant found that the prime rib was held at an improper temperature.