Laboratory testing by the South Dakota Department of Health has identified Clostridium perfringens as the cause of the outbreak associated with the Pierre-Mitchell high school boys’ basketball game held in Pierre, Jan. 31.

KSFY ABC reports the investigation, which included voluntary questionnaires, implicated tacos as the source food of the outbreak; of those completing questionnaires, 75 per cent who ate the tacos reported becoming ill.

The outbreak follows a similar C. perfringens outbreak in Las Vegas before Christmas in which ham was held at improper temperatures and inadequately reheated, sickening at least 21 people. As noted in the Las Vegas outbreak, the majority of C. perfringens outbreaks are often the results of improperly cooled food or food held at room temperature for extended periods.