One person is dead and 10 have been hospitalized due to an E. coli outbreak linked to McDonald's Quarter Pounders, according to the CDC. (Photo credit: Hyoung Chang/Denver Post/Getty Images via CNN Newsource)

(CNN) — The US Centers for Disease Control and Prevention issued a food safety alert Tuesday regarding an E. coli outbreak that it says is linked with McDonald’s Quarter Pounders.

At least 49 illnesses have been reported across 10 states, including one death of an older person. Ten people have been hospitalized, including a child who had hemolytic uremic syndrome, a serious complication that can develop from an E. coli infection. Most of the illnesses are in Colorado and Nebraska.

Most of the people who became ill reported eating McDonald’s Quarter Pounder sandwiches, the CDC says.

The agency says that the investigation is “fast-moving” and that information reviewed by the US Food and Drug Administration shows that slivered onions are a likely source of contamination.

McDonald’s has stopped using the onions as well as quarter-pound beef patties in several states while the investigation continues, the CDC says. According to the agency, the beef patties are used only for the Quarter Pounders, and the slivered onions are used primarily for the Quarter Pounder and not other items.

McDonald’s said in a statement that the initial investigation findings linked the onions to “a single supplier that serves three distribution centers.”

“We are working in close partnership with our suppliers to replenish supply for the Quarter Pounder in the coming weeks (timing will vary by local market),” it said. “In the meantime, all other menu items, including other beef products (including the Cheeseburger, Hamburger, Big Mac, McDouble and the Double Cheeseburger) are unaffected and available.”

According to the FDA, McDonald’s has removed the slivered onions and quarter-pound patties from stores in Colorado, Kansas, Utah, Wyoming and portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico and Oklahoma. In other states, Quarter Pounder burgers may not be available.

However, the CDC also notes that the outbreak may go beyond those states.

People with E. coli infections may have symptoms including severe stomach cramps, diarrhea, fever and vomiting. Symptoms of infection usually begin three or four days after swallowing the bacteria. Although most people who become ill recover without treatment within a week, others can develop serious kidney problems and require hospitalization.

Anyone who becomes ill after eating a McDonald’s Quarter Pounder should get medical attention and tell the provider what they ate, the CDC says.

McDonald’s said in its statement that “serving customers safely in every single restaurant, each and every day, is our top priority” and that it will continue working with the CDC on the investigation.

McDonald’s stock price dropped precipitously in after-hours trading as news of the outbreak broke.

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