Tainted irrigation water appears to be the source of a national food poisoning outbreak linked to romaine lettuce, health officials said.
About 200 people were sickened in the E. coli outbreak and five people died. The outbreak, which started in the spring, is now over, the Centers for Disease Control and Prevention said.
The illnesses in 36 states were previously traced to romaine lettuce grown in Yuma, Arizona, which provides most of the romaine sold in the U.S. during the winter.
On Thursday, officials said the outbreak strain of E. coli bacteria was found in an irrigation canal in the Yuma area. They are still investigating how the bacteria got into the canal and whether there was contamination elsewhere. They declined to give details about the canal, including its location, until a report can be completed.