( Courtesy Evergreens )

The King County (Wash.) Public Health Department continues to work with state and federal agencies to find the origin of E. coli that made 13 people ill.

The outbreak, “potentially associated” with six Evergreens restaurants in Seattle, is not related to the national E. coli outbreak that’s caused more than 100 illnesses across the U.S. and has been linked to romaine lettuce grown in the Salinas, Calif., area.

The county health department reported 7 cases on Nov. 22, and updated that to 13 cases on Dec. 6. All patients have since recovered, but the investigation into the source continues, according to the update.

Although the King County Public Health Department identified an Evergreens employee who “experienced symptoms consistent with an E. coli infection” after eating at the restaurant, the employee was not tested and there’s no evidence the person is the source of the outbreak, according to the Dec. 6 notice.

The restaurants discarded all romaine lettuce, but samples of “various produce” tested at two of the Evergreens were negative for pathogens, according to the notice.

The county health department is working with the Washington State Department of Agriculture and the Food and Drug Administration to trace back ingredients consumed by those who became ill.

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