WASHINGTON - Public health officials are now telling consumers to avoid all types of romaine lettuce that may have come from Yuma, Ariz., because of an E. coli outbreak linked to the vegetable that has spread to at least 16 states and sickened at least 60 people, including eight inmates at an Alaska prison.

The Centers for Disease Control and Prevention said Friday that new information about the illnesses in Alaska led them to expand a warning beyond chopped romaine to include any type of romaine lettuce, including whole heads and hearts of romaine. The inmates who became sick at the Anvil Mountain Correctional Center in Nome ate lettuce from whole heads of romaine grown in Yuma, the CDC said.

Although the exact source of the tainted lettuce hasn’t been identified, federal officials have said information indicates the contaminated lettuce was grown in the southeast corner of Arizona. Of those who have been sickened, at least 31 people have been hospitalized, including five who developed a type of potentially life-threatening kidney failure known as hemolytic uremic syndrome. No deaths have been reported.

No common grower, supplier, distributor or brand has yet been identified. Symptoms of infection include bad stomach cramps, diarrhea and vomiting. Occasionally, more serious complications can occur, including kidney failure.

Consumers anywhere in the United States who have store-bought romaine at home, including salads and salad mixes containing that lettuce, should throw it away immediately if it is from the Yuma area, federal health officials said — even if some had already been eaten with no ill effects.

Officials also said consumers should throw away any lettuce from Yuma if they’re unsure what kind it is. Consumers also should not buy or eat romaine lettuce at a grocery store or restaurant unless they can confirm it is not from the Yuma area.

The number of cases of illness has grown in the past several days. On Tuesday, a 66-year-old woman in New Jersey, Louise Fraser, filed a lawsuit in federal court against Panera Bread after claiming she ate contaminated romaine lettuce there and then had to be hospitalized for two weeks.

Among the hardest hit states are Pennsylvania, with 12 reported cases, and Idaho, with 10.

Romaine lettuce is sometimes packed in the field and shipped directly to restaurants or grocery stores. Other times, it is taken to a central processing plant, where it is packed under different brands before being sent to retailers, according to Bill Marler, a Seattle-based personal injury attorney who focuses on food-borne illness litigation and is representing several people sickened in the outbreak, including Fraser.

The different ways that romaine lettuce is harvested could make identifying the specific origin of contamination more difficult, Marler said.