Story highlights At least 39 separate recalls have been issued since May

The manufacture of sunflower kernels resumed Wednesday

(CNN) Some Clif Bar trail mix and energy bars are the latest products to be voluntarily recalled because they contain sunflower kernels that may have been contaminated with listeria, the company said Thursday.

At least 39 separate recalls have been announced since May 3 by companies that use sunflower kernels, the meat of the sunflower seed, supplied by SunOpta, in products distributed throughout the U.S. These include an array of salads, trail mixes and snack bars. Multiple products are included in each of the recall announcements.

No illnesses have been linked to the potentially contaminated sunflower kernels, according to the company.

Symptoms of listeriosis infection include fever, muscle aches and gastrointestinal illness, such as diarrhea. It can also lead to meningitis. Pregnant women, newborns, older adults and anyone with a weakened immune system is most at risk for infection. Cervical infections caused by listeriosis in pregnant women may result in stillbirth or spontaneous abortion during the second or third trimesters.

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