ATLANTA — The CDC is investigating after people have been reporting feeling sick after eating McDonald’s Quarter Pounder hamburgers at locations across the United States.

The CDC says there have been 49 cases in 10 states reported of symptoms of E.coli including 10 hospitalizations and one death. Most illnesses have been reported in Nebraska and Colorado, officials say.

According to the CDC, “McDonald’s is collaborating with investigation partners to determine what food ingredient in Quarter Pounders is making people sick. McDonald’s stopped using fresh slivered onions and quarter pound beef patties in several states while the investigation is ongoing to identify the ingredient causing illness.”

People who experience E-coli symptoms have severe stomach cramps, diarrhea (often bloody), and vomiting. Some people may develop kidney problems, and need to be hospitalized, the CDC says. Officials add that people may also have a fever of higher than 102°F, dehydration including dry mouth and throat, or feeling dizzy when standing up.

It is unknown which specific food ingredient is contaminated, according to the CDC.

The CDC says “Quarter Pounder hamburgers will not be available temporarily in some states. Investigators are working to confirm which ingredient in these hamburgers is making people sick and if it went to other restaurants or stores.”