Consumer Reports is warning Americans to stay away from romaine lettuce after dozens of cases of E. coli in the US and Canada left two people dead. And while the Centers for Disease Control hasn't gone that far, it is looking for the source of the E. coli, which sickened people in 13 states between Nov. 15 and Dec. 8, CNN reports. "Based on the Canada investigation, romaine lettuce seems like the most likely source there," the CDC's Ian Williams says. "Unfortunately, we have not been able to find common lettuce brands or common stores." Other leafy greens have also been implicated as a potential source. E. coli cases were reported in California, Connecticut, Illinois, Indiana, Michigan, Nebraska, New Hampshire, New York, Ohio, Pennsylvania, Virginia, Vermont, and Washington.