NEW YORK (AP) – U.S. health officials on Friday told people to avoid romaine lettuce grown in Salinas, California, because of another food poisoning outbreak.

The U.S. Food and Drug Administration is investigating an E. coli outbreak that has sickened 40 people in more than a dozen states. The agency said its inquiry led investigators to farms in Salinas and that they were looking for the contamination source.

15 states including Washington now report illnesses.

According to the Centers for Disease Control and Prevention, as of Friday there is one case in Washington State.

The officials urged people not to eat the leafy green if the label doesn’t say where it was grown. They also urged supermarkets and restaurants not to serve or sell the lettuce, unless they’re sure it’s grown elsewhere.