LATEST: CDC continues to investigate listeria linked to caramel apples; at least six people have died

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(CNN) — A sweet treat has turned potentially deadly for dozens of people in multiple states.

At least six people have died after eating caramel apples that may have been infected with Listeria monocytogenes.

“Listeriosis contributed to three of these deaths and it is unclear whether it contributed to two others. The sixth death was unrelated to listeriosis,” according to a Food and Drug Administration release.

Some 32 people have become infected with the deadly bacterium in 11 states, according to the Centers for Disease Control and Prevention.

The Public Health Agency of Canada has also identified two cases of listeriosis in Canada and the samples show the same DNA fingerprints as the American cases.

Of the people who have gotten sick, 10 were pregnant. Pregnant women are 10 times more likely to get listeriosis after eating infected food.

Of the rest of the cases, three were children who were otherwise healthy, the CDC said.

Symptoms of listeriosis infection include muscle aches, headache, stiff neck, confusion, loss of balance, fever and convulsions. Typically, symptoms begin three to 70 days after eating the tainted food.

To date 23 of the 26 people who were interviewed about their illnesses remembered eating commercially produced, prepackaged caramel apples before they got sick.

Most of the people who got sick with this outbreak saw the doctor in late October and November.

Investigators are still trying to determine all the contributing factors in the case. To date caramel apple brands named in interviews include Happy Apple, Carnival and Merb’s Candies. Investigators are also looking at other companies for the source of the contamination.

In the meantime, the CDC is warning consumers who may have bought caramel apples with toppings like nuts, chocolate or sprinkles not to eat them, at least not until investigators figure out the source of the contamination.

Three companies — Happy Apple Company of Washington, Missouri; California Snack Foods, of El Monte, California; and Merb’s Candies of St. Louis, Missouri — have issued voluntary recalls of their caramel apples.

The companies have used apples from Bidart Bros. The FDA traced the distribution of the apples eaten by eight people who got sick in the outbreak. Bidart Bros. is the only apple grower that supplied both Happy Apple Company and Merb’s Candies.

On December 22, Bidart Bros. recalled Granny Smith apples it sold in 2014 to caramel apple companies.

Lab results for Listeria monocytogenes done in a joint inspection of the firm by the FDA and the California Department of Public Health turned up positive. Lab tests are ongoing.

On January 6, Bidart Bros. expanded its voluntary recall to include Gala apples shipped from the company’s Shafter, California, packing facility in 2014.

There are about 1,600 cases of listeriosis reported in the United States every year. This kind of infection kills about 260 people annually, according to the CDC.

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