Crowe SJ, et al. - Herein, the authors examined an outbreak of Shiga toxin–producing Escherichia coli (STEC) serogroup O121 and O26 infections associated with contaminated flour from a large domestic producer. Based on the findings, raw flour was implicated as the source of an outbreak of STEC infections. Despite being a low-moisture food, raw flour could be a vehicle for foodborne pathogens.