(CNN) — A listeria outbreak linked with ready-to-eat meat and poultry products from Yu Shang Food Inc. has caused 11 illnesses in four states, with nine hospitalizations and one death, according to the US Centers for Disease Control and Prevention.

The Spartanburg, South Carolina, company is recalling more than 72,000 pounds of meat and poultry products because of possible listeria contamination. All ready-to-eat products produced before October 28 are included, the US Department of Agriculture’s Food Safety and Inspection Service says. The products were shipped to retailers nationwide and were available online.

Routine testing and follow-up conducted last month by the Food Safety and Inspection Service confirmed that the products were positive for Listeria monocytogenes, and sequencing is underway to determine whether there’s a match to the bacteria strain involved in the illness outbreak.

Yu Shang Food has not responded to CNN’s request for further comment.

Seven illnesses have been reported in California, two in Illinois and one each in New York and New Jersey, the CDC says.

“In California, one pregnant person and their twins were sick and both infants died,” the agency said. “Listeria was found in a sample from the mother and from one of the twin infants, but it could not be found in a sample from the other infant. Because of this, only the mother and one twin are included as confirmed cases in this outbreak. One other Listeria illness was reported in an infant who was sick and recovered.”

Officials say the true number of cases is probably higher because some sick people recover without medical care and because it usually takes a few weeks to determine if a case is part of an outbreak.

Anyone who has these recalled products should not eat them. Throw them out or return them to where you bought them. Clean any containers or surfaces that may have come into contact with recalled foods.

Listeria bacteria causes listeriosis, the third leading cause of death from foodborne illness in the United States. Symptoms can include fever, muscle aches and fatigue. An infection can also cause a stiff neck, a headache, confusion or seizures. Those most at risk of severe outcomes are older adults, pregnant women and people with weakened immune systems.

If you develop these symptoms and may have eaten recalled products, get medical care right away.

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