In a sweeping move, the CDC is expanding its warning to consumers to cover all types of romaine lettuce from the Yuma, Arizona growing region after the food was linked to an E. coli outbreak. And, it’s telling consumers to avoid romaine lettuce all together, because it can be so hard to track its growing region.

The news comes after the CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration said they were investigating the multistate outbreak of Shiga toxin-producing Escherichia coli O157:H7 (E. coli O157:H7) infections.

Specifically, 53 people infected with the outbreak strain of E. coli O157:H7 have been reported from 16 states and 31 people have been hospitalized, including five people who have developed a type of kidney failure called hemolytic uremic syndrome. No deaths have been reported.

The expanded warning is based on information from newly reported illnesses in Alaska and it now includes whole heads and hearts of romaine lettuce, in addition to chopped romaine and salads and salad mixes containing romaine.

The CDC updated its advice as a result of new information gained during its investigation, says Bob Whitaker, chief science and technology officer, Produce Marketing Association. Specifically, the Alaska Department of Health and Social Services reports that a correctional facility in that state received whole head romaine grown in the Yuma area.

“It is important to know that romaine sourced from coastal and central California, Florida, and central Mexico are not part of the current extended consumer alert,” Whitaker says. “We have and will continue to offer our food safety expertise and industry knowledge to the agencies, to help them get to the bottom of this problem as soon as possible. Meanwhile, we continue to keep those impacted by this outbreak in our thoughts. Our consumers’ health and safety are of the utmost importance to the entire fresh produce industry.”

The CDC says that unless the source of the product is known, consumers anywhere in the United States who have any store-bought romaine lettuce at home should not eat it and should throw it away, even if some of it was eaten and no one has gotten sick.

“Product labels often do not identify growing regions; so, throw out any romaine lettuce if you’re uncertain about where it was grown,” the CDC says. “This includes whole heads and hearts of romaine, chopped romaine, and salads and salad mixes containing romaine lettuce. If you do not know if the lettuce is romaine, do not eat it and throw it away.”

Also, restaurants and retailers should not serve or sell any romaine lettuce from the Yuma, Arizona growing region.

At this time, no common grower, supplier, distributor, or brand has been identified with the outbreak. The investigation is ongoing, and CDC will provide updates when more information is available.