The U.S. Food and Drug Administration said Saturday that federal, state and local officials are investigating the outbreak linked to foods produced by Fresh & Ready Foods LLC of San Fernando, California. The FDA says the 10 people who fell ill were in California and Nevada, and required hospitalization.

The agency said the products were sold in Arizona, California, Nevada and Washington at locations including retailers and food service points of sale, including hospitals, hotels, convenience stores, airports and by airlines.

Listeria symptoms usually start within two weeks of eating contaminated food. Mild cases can include fever, muscle aches, nausea, tiredness, vomiting and diarrhea, while more severe symptoms may include headache, stiff neck, confusion, loss of balance and convulsions.

Federal officials said they started investigating the recent outbreak last year but didn’t have enough evidence to identify a source of the infections. They said the investigation was reopened in April when FDA investigators found listeria in samples collected from Fresh & Ready Foods that matched the strain from the outbreak.

Fresh & Ready Foods said in a news release that it took immediate corrective actions including removing equipment to address the issue.

The FDA found that six of the 10 people who got sick had been hospitalized before becoming ill with listeria. The FDA found that items made by Fresh & Ready Foods had been served in at least three of the health care facilities where the patients had been previously treated.

The Centers for Disease Control and Prevention said that the test samples from sick patients were collected from December 2023 to September 2024.

Fresh & Ready voluntarily recalled several products, which can be identified by “use by” dates ranging from April 22 to May 19 of this year under the brand names Fresh & Ready Foods, City Point Market Fresh Food to Go and Fresh Take Crave Away.