The U.S. Food and Drug Administration Monday joined Idaho public health officials in an unusual warning to consumers, advising them not to eat alfalfa sprouts or spicy sprouts from Evergreen Produce, a growing operation in Moyie Springs, Idaho that has been in business for 23 years.

An outbreak that has sickened 20 people in five states with Salmonella Enteritidis — which is not related to the outbreak of E. coli O104:H4 attributed to sprouts in Europe — may be linked to the Idaho-grown sprouts, the FDA said, echoing similar warnings issued last week by the Idaho Department of Health. Idaho officials said six of the case patients reported eating the sprouts.

FDA said it is investigating the outbreak along with the Centers for Disease Control and Prevention (CDC) and public health agencies in Idaho, Montana, New Jersey, North Dakota and Washington state.

The FDA said one of the 20 people has been hospitalized.

“The strain of S. Enteritidis is rarely seen at this frequency,” the agency said in a news release, without further explanation.

The FDA did not respond to inquiries about why the suspect sprouts aren’t being recalled. Its news release said only that the agency is “also working with state authorities to take appropriate action to address any product that may be remaining on the market.”

The agency usually issues such a warning when a food producer refuses to voluntarily recall a potentially contaminated product.  Although the FDA now has the authority to impose mandatory recalls, it typically tries to work cooperatively with food producers to ensure that possibly dangerous food is removed from the market.

In <a href="”>an interview with the Spokesman Review in Spokane, WA., the owner of Evergreen Produce said she has temporarily stopped selling alfalfa sprouts but wants “concrete evidence” that her sprouts are causing the problem.

She told the newspaper, “Our company’s name has been smeared and it makes me think, the way they are going about this, that maybe they just want to shut us down. We’re just hanging by a thread.”

Evergreen Produce, according to the report, sells about 6,000 pounds of mung beans, clover, broccoli and alfalfa sprouts each week.

The alfalfa sprouts or spicy sprouts were sold in plastic bags labeled “Evergreen Produce” or “Evergreen Produce Inc.” The alfalfa sprouts are packaged in 4-ounce and 16-ounce plastic bags with pre-printed labels. They are also packaged in 1-pound and 5-pound plastic bags with stick-on labels. The spicy sprouts are packaged in 4-ounce plastic bags with pre-printed labels and 1-pound plastic bags with stick-on labels.

FDA said the suspect sprouts should be discarded in a sealed container so people and animals, including wild animals, cannot eat them.