Romaine lettuce is off the menu of US households and restaurants, health authorities ordered on Saturday after a spreading E.coli outbreak infected 53 people in 16 states.
The warning from the Centers for Disease Control and Prevention covers all types of romaine lettuce from in and around Yuma, Arizona.
"Do not buy or eat romaine lettuce at a grocery store or restaurant unless you can confirm it is not from the Yuma, Arizona growing region," the CDC said on its website.
"Throw out any romaine lettuce if you're uncertain about where it was grown."
The CDC said no deaths have been reported but 31 people have been hospitalized, including five who developed a type of kidney failure.