The Harvey's Restaurant in North Bay, Ontario, Canada, was closed in October due to an outbreak of E. coli O157:H7 infections associated with the restaurant. The investigation concluded that the cause of the outbreak was inconsistent cleaning. The outbreak was likely initiated by contaminated onions. Inconsistent cleaning of the onion dicer may have perpetuated the contamination for several days. Onion was considered the likely source of illnesses on the basis of a case control analysis and not on the basis of environmental or food testing.