Recalled Smoked Mozzarella Pasta Salad.

More products sold at Kroger stores have been recalled as the Food and Drug Administration (FDA) continues to investigate a multi-state listeria outbreak.

The 15-state outbreak has sickened at least 20, killing four, since the Centers for Disease Control and Prevention (CDC) and the FDA began investigating cases of listeria poisoning, or listeriosis, in September. The illnesses have been traced back to pastas used in ready-to-eat products at grocery stores like Walmart and Kroger nationwide, prompting a cascade of developing recalls.

Kroger, along with competing grocer Giant Eagle, has added yet another set of items to its growing recall list on Oct. 4 as the investigation continues.

Here's what to know about the latest products added to the recall list.

Newly recalled Kroger products

Two recalled pasta salads were sold at the Kroger Family of Stores in Alabama, Alaska, Arizona, Arkansas, California, Colorado, Georgia, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, Ohio, Oregon, South Carolina, Tennessee, Texas, Utah, Washington and West Virginia.

  • Basil Pesto Bowtie Pasta Salad of various weights sold at deli counters and in Grab-n-Go packages between Sept. 6 and Oct. 2 with UPC codes 217573-10000 and 217573-20000.
  • Smoked Mozzarella Penne Salad of various weights sold at deli counters and in Grab-n-Go packages between Aug. 29 and Sept. 2 with UPC code 227573-10000.

The salads were sold at multiple stores under the Kroger banner, including Kroger, Baker’s, City Market, Dillons, Fred Meyer, Fry’s, Gerbes, King Soopers, Payless, Ralphs and Smith’s.

Giant Eagle, another grocery chain, also recalled the same Smoked Mozzarella Penne Salad sold starting on Sept. 25 at Giant Eagle and Market District locations across western Pennsylvania, Ohio, Maryland and Indiana.

What to do with recalled pasta meals

Both the CDC and FDA advise returning affected products to the place of purchase for a refund or tossing them in the trash.

Wash and sanitize bowls, cups, storage containers and other surfaces that may have come into contact with the recalled products. Always thoroughly wash your hands after handling and preparing food, especially raw or uncooked products.

4 dead in listeria outbreak, cases reported in 15 states

The listeria outbreak was first announced in June when the CDC began investigating reports of illness.

As of Sept. 25, there were 20 confirmed cases of listeria poisoning linked to the outbreak, the CDC reported in its latest update on Oct. 6. Of those, 19 people were hospitalized and four died. In one case, a pregnant woman experienced fetal loss as a result of a related infection.

Deaths occurred in Utah, Illinois, Michigan, and Texas. Associated infections were confirmed in the following states: California (2 cases), Florida (1 case), Illinois (1 case), Indiana (1 case), Louisiana (2 cases), Michigan (2 cases), Minnesota (1 case), Missouri (1 case), Nevada (1 case), North Carolina (1 case), Ohio (1 case), South Carolina (1 case), Texas (3 cases), Utah (1 case) and Virginia (1 case).

The numbers are only the known cases and likely do not represent the full extent of the outbreak, according to the CDC.

What are the symptoms of listeria poisoning?

Listeria poisoning is a foodborne bacterial infection most commonly caused by the bacterium listeria monocytogenes, according to the CDC. It is considered a serious condition and can be dangerous or life-threatening, especially to older adults, people with weak immune systems and pregnant women.

Per the CDC, symptoms include:

  • Fever
  • Muscle aches
  • Headache
  • Stiff neck
  • Confusion
  • Loss of balance
  • Convulsions
  • Diarrhea
  • Other gastrointestinal symptoms
  • Miscarriage, stillbirth, premature delivery and/or life-threatening infection of newborn infants
  • Death

People in higher-risk categories who experience flu-like symptoms within two months of consuming contaminated food should seek medical attention, according to the CDC.

This article originally appeared on USA TODAY: Kroger recalls more pasta dishes amid multistate listeria outbreak. See which ones.

Reporting by Mary Walrath-Holdridge, USA TODAY / USA TODAY

USA TODAY Network via Reuters Connect