(AP) — Reser’s Fine Foods Inc. has voluntarily expanded a recall of packaged salads from its factory in Topeka, Kan.

The company based in Beaverton, Ore., said it took the step Saturday because the products distributed nationwide and in Canada may be contaminated with listeria, which can cause serious illness.

Symptoms of listeria include fever, headache, abdominal pain and diarrhea. People with weak immune systems, such as young children, elderly people and others can die. Pregnant woman can suffer miscarriage or stillbirth.

The recall was first announced Friday.

The company said in a statement on its website that there have been no confirmed illnesses linked to the products. Consumers were advised they could throw away recalled products or take it back where they bought it for a refund.

The products include potato, pasta, tuna and egg salads and others sold under the Reser’s name and others.

Reser’s said the packages are marked with a plant identifier code of 20 next to the best-by-date. About 450 products are listed on the Resers.com website and were sold under names that include Safeway Deli Counter, Walmart and SYSCO, as well as many others. The expiration dates range from Oct. 11 to Feb. 6, 2014.

Reser’s would not respond to questions about how the contamination was discovered, how extensive it was, whether the plant remained operating, or what kind of losses the recall represented.

Food and Drug Administration spokeswoman Juli Ann Putnam said FDA generally does food inspections, but companies sometimes do their own. She said the agency was referring specific questions to Reser’s, as it generally does in cases of voluntary recalls.