WASHINGTON (AP) — Federal health officials announced the death of an infant in California as they investigate an outbreak of listeria infection linked to ready-to-eat meat and poultry products.

At least 10 other people have become ill Yu Shang Food Products which includes chicken feet, duck neck, beef leg, and pork hock, US Centers for Disease Control reported Friday.

Yu Shang Food, Inc., of Spartanburg, South Carolina, recalled more than 72,000 pounds of meat and poultry products linked to the outbreak, according to United States Department of Agriculture.

The food was shipped to stores across the country and available online, and illnesses have been reported in California, Illinois, New York and New Jersey. The problem was discovered in October after routine testing detected listeria in food and the production environment, the CDC said in its press release.

Of the 11 people who fell ill, nine were hospitalized, the US Centers for Disease Control said. A California woman pregnant with twins became ill and both infants died, the CDC said, but listeria was only found in a sample from one of the infants, so the child and mother were included in the count but the other infant was “t.

Interviews with people who were sick and laboratory findings pointed to the Yu Shang Food products.

Even if the foods have been recalled, some may still be in consumers’ refrigerators or freezers. The products must be discarded or returned to the place of purchase. Refrigerators, containers and other surfaces that may have touched the food must be cleaned and disinfected.

People get sick from listeria poisoning when they eat food contaminated with the bacteria. Symptoms can be mild and include fever, muscle aches, nausea, vomiting and diarrhea. More serious ailments can include headache, stiff neck, confusion, loss of balance and convulsions.

Listeria poisoning is tricky, because symptoms can start quickly, within hours or days of eating contaminated food. But they can also take weeks or up to three months to appear. Those who are most vulnerable to getting sick are the very young, people over 65 and those with weakened immune systems or who are pregnant.

Another listeria outbreak linked to recalled Boar’s Head deli meats has been terminated, CDC officials said this week. That outbreak killed 10 people this summer and sickened dozens more.