The warning was spurred by an outbreak of E. coli that has now sickened 53 people in 16 states. Five people that have been infected have developed a type of kidney failure called hemolytic uremic syndrome. No deaths have yet been reported.
They warn all consumers to throw all romaine away under the infection is controlled.
The CDC noted that product labels often don't identify growing regions; any lettuce not marked should be tossed, even if part of it has been eaten and nobody became ill.
The CDC says the new information comes Alaskans suffering from E. coli who ate whole head romaine lettuce from the Yuma region.
Consumers as well as restaurants and retailers are advised to throw away any lettuce if they can't confirm where it's from. However, the investigation now not only encompasses chopped romaine lettuce, but all romaine lettuce from the Yuma, Arizona region.
Romaine lettuce is sometimes packed in the field and shipped directly to restaurants or grocery stores.
The Center for Disease Control and Prevention asked Americans on Friday to throw away romaine lettuce unless they could clearly identify where it came from.
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Symptoms of E. coli, which typically begin two to eight days after consuming the bacteria, include severe stomach cramps, diarrhea and vomiting.
The CDC is actively investigating the development of this outbreak.
The E. coli spreading through the states is "toxin-producing", the CDC states - specifically a toxin known as Shiga. Occasionally, more serious complications can occur, including kidney failure.
One case linked to the outbreak has been identified in IL. The gap between when someone gets sick and when it is reported to public health agencies can be up to three weeks, according to the agency.
Obviously, if you grow your own romaine lettuce or know exactly where it was grown (and it's not anywhere near Yuma, Arizona) feel free to continue to indulge in the leafy vegetable to your heart's content.