Shredded iceberg lettuce appears to be the most likely culprit responsible for the Taco Bell E. coli outbreak in the Northeast, officials at the Food and Drug Administration said. Their conclusions were based on statistics derived from a case-controlled study conducted by the Centers for Disease Control and Prevention. Cheddar cheese and ground beef were also statistically associated with ill persons in the study, said Christopher Braden, medical epidemiologist for the CDC, but shredded lettuce remains the focus of the investigation. The outbreak, which caused more than 70 cases of illness, appears to be over, officials said. Also, there was no indication the outbreak of foodborne illnessess associated with Taco John‘s restaurants in Iowa was linked to the Taco Bell case, officials said.