Lettuce grown in Monterey County has been linked to five cases of E. coli bacteria poisoning at a Wendy’s restaurant in Ogden, Utah, during a three-day period in late June, reports CBS Channel 5 in Salinas.

"The only food item that was shared by all of these cases was iceberg lettuce from this Wendy’s store,” Weber-Morgan Health Department Officer Gary House said. "The lettuce was the common source.”

The Wendy’s restaurant at the center of the outbreak was thoroughly inspected and no health violations were found.

Wendy’s staff told the health department that the lettuce came from Monterey County.

Because Wendy’s regularly disposes of its unused lettuce, however, health officials could not test samples of the lettuce from the three-day period to positively confirm the origin of the E. coli, according to House.

California Department of Health Services spokeswoman Patti Roberts cautioned that just because lettuce from Monterey County was found to be a common source in the outbreak does not mean that the E. coli originated with the lettuce.

The Department of Health Services has not begun an investigation of Monterey County’s lettuce crop in connection with the Utah E. coli outbreak at this point.