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

The company, based in Beaverton, said it took the step recently because the products distributed nationwide and in Canada could 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 from the illness. 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, however, were advised they could throw away recalled products or take the items back where they bought them for a refund.

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

The company 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 or how extensive it was.

— From staff and wire reports