(CNN) -- Citing a potential health risk, the California Department of Public Health warned consumers Friday to not eat certain bagged salads manufactured by River Ranch Fresh Foods and sold under various names.The company, based in Salinas, California, voluntarily recalled the salads "after routine sampling detected Listeria Monocytogenes in two packages of shredded iceberg lettuce purchased from retail locations in California and Colorado," the health department said in a news release.No illnesses have been reported, it said.The affected salads have been distributed to outlets across the country under the brand names River Ranch, Farm Stand, Hy-Vee, Marketside, Shurfresh, The Farmer's Market, Cross Valley, Fresh n Easy, Promark and Sysco, it said.River Ranch is a wholly owned subsidiary of Taylor Farms, also of Salinas. Neither company responded to calls for comment.A spokeswoman for the health department said it was not immediately clear how large the recall would ultimately be. "We're looking into that right now," Heather Bourbeau said.The bacteria are commonly found in soil and water.Symptoms of infection may include fever and muscle aches, sometimes preceded by diarrhea or other gastrointestinal symptoms, according to the Centers for Disease Control and Prevention. In addition, they may include a headache, a stiff neck, confusion, a loss of balance and convulsions.Infants, the elderly and people with weak immune systems are at highest risk for severe illness and death. Among pregnant women, the bacteria can lead to miscarriage or stillbirth, premature delivery or infection of the newborn.