Romaine lettuce is unsafe to eat after being linked to a multi-state E. coli outbreak, the Centers for Disease Control and Prevention said Tuesday.

The CDC is calling for all U.S. consumers, restaurants and retailers to dispose of all romaine lettuce. Those who have any type of romaine lettuce in the fridge — including whole heads, romaine hearts, boxes of romaine or salad mixes with romaine — are asked to throw it away, even if some of it was eaten without leading to illness. Restaurants and retailers have been warned to not serve any form of romaine lettuce to customers.

The CDC says it’s calling for people across the U.S. to avoid romaine lettuce because it has not yet identified the source of the contaminated green.

The warning comes as romaine lettuce is linked to 32 cases of E. coli reported from 11 states. At least 13 people were hospitalized for illnesses that began between Oct. 8 and Oct. 31, the CDC says. Most of the E. coli cases so far come from California, which reported 10. Michigan has the second-most reported cases, with seven. Other states, including Connecticut, Illinois, Massachusetts, Maryland, Michigan, New Hampshire, New Jersey, New York, Ohio and Wisconsin, each reported between 1 and 3 cases of E. coli.

Canada’s Public Health Agency also reported 18 people became ill from the same strain of E. coli. No deaths have been reported.

The romaine-linked E. coli outbreak follows one earlier this year, when five people died from E. coli contaminated romaine lettuce from Yuma, Ariz.

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Write to Mahita Gajanan at mahita.gajanan@time.com.