The strain of E. coli bacteria that contaminated romaine lettuce and was tied to the deaths of five people was found in a tainted irrigation canal in Arizona, federal officials said on Thursday.



The outbreak appeared to be over, more than three months after the first illnesses were recorded, the Centers for Disease Control and Prevention said.

Samples of canal water in the Yuma area of Arizona were found to contain the same genetic strain of E. coli that caused the outbreak, Dr. Scott Gottlieb, commissioner of the federal Food and Drug Administration, said in a statement.

When eight inmates at an Alaska prison got sick, F.D.A. investigators traced the illness back to whole-head romaine lettuce that was harvested from Harrison Farms in the Yuma area. Health officials said the lettuce that caused the national outbreak was linked to many farms in the region. Representatives of Harrison Farms could not be reached for comment on Saturday.