The U.S. Food and Drug Administration on Thursday recalled a brand of soft-serve ice cream after linking it to listeria cases in Pennsylvania and New York.

The product, Soft Serve On The Go ice cream cups, was distributed in several states, the recall said, and two people have been hospitalized for their illness.

The outbreak involves Listeria monocytogenes infections potentially linked to the ice cream cups, which are produced by Real Kosher Ice Cream of Brooklyn, N.Y.

Both patients reported eating the vanilla chocolate ice cream before they became ill. An unopened sample from the home of one of the people who became ill was positive for L. monocytogenes. Genetic analysis is still necessary, to determine if the strain found is the one implicated in this outbreak.

Real Kosher Ice Cream has temporarily stopped production of these products and is cooperating with the investigation, the FDA said.

Voluntarily recalled flavors are vanilla chocolate, razzle, caramel, parve vanilla chocolate, strawberry mango and peanut butter. Other products may be added.

The ice cream was distributed in California, Colorado, Connecticut, Washington, D.C., Delaware, Florida, Illinois, Massachusetts, Maryland, Michigan, Minnesota, North Carolina, New Hampshire, New Jersey, New York, Ohio, Oregon Pennsylvania, Virginia and West Virginia.

Listeriosis symptoms can start within a few hours of eating a contaminated product or as long as two or three days later. More severe forms of listeriosis can take three days to three months to develop. Mild symptoms may include a fever, muscle aches, nausea, vomiting and diarrhea, while a severe form of listeriosis can include headache, stiff neck, confusion, loss of balance and convulsions, the FDA said.

People, retailers and restaurants should not eat, sell or serve these products. the agency added. Throw the recalled product away or return to place of purchase for a full refund.

Listeria is most likely to sicken pregnant people and newborns, adults 65 or older and people with weakened immune systems. While other people can be infected, they rarely become seriously ill. Pregnant people typically experience fever, fatigue and muscle aches, but infection during pregnancy can lead to miscarriage, stillbirth, premature delivery or a life-threatening infection of the newborn, the FDA said.

Someone who thinks they may have symptoms of listeriosis should call their healthcare provider immediately.