E. coli food poisoning linked to McDonald鈥檚 Quarter Pounder hamburgers has sickened at least 49 people in 10 states, including one person who died and 10 who were hospitalized, said Tuesday.

The death was reported in an older person in Colorado, and one child has been hospitalized with severe kidney complications, the U.S. Centers for Disease Control and Prevention reported.

Infections were reported between Sept. 27 and Oct. 11, in Colorado, Iowa, Kansas, Missouri, Montana, Nebraska, Oregon, Utah, Wisconsin and Wyoming. Colorado has the most cases, 27, followed by Nebraska with nine.

Everyone interviewed in connection with the outbreak had reported eating at McDonald鈥檚 before falling ill and most mentioned eating Quarter Pounder hamburgers, the CDC said. The U.S. Agriculture Department, the Food and Drug Administration and state health officials are also investigating.

The specific ingredient tied to the outbreak has not been identified, but investigators are focused on onions and beef. McDonald鈥檚 reported to the CDC that it had removed slivered onions and beef patties used for Quarter Pounders from stores in the affected states. The burgers may be temporarily unavailable in those states.

are harbored in the guts of animals and found in the environment. Infections can cause severe illness, including fever, stomach cramps and bloody diarrhea. People who develop symptoms of E. coli poisoning should seek health care immediately and tell the provider what they ate.

The Associated Press has reached out to McDonald鈥檚 for comment.

The news comes in an already tough year for the Chicago-based chain. Its global same-store sales in nearly four years in the second quarter as inflation-weary customers skipped eating out or chose cheaper options. The company responded with a $5 meal deal, which was introduced at U.S. restaurants in late June and was recently . The deal doesn鈥檛 include the Quarter Pounder.

McDonald鈥檚 shares dropped 9% in after-hours trading Tuesday after the CDC鈥檚 announcement.

The type of bacteria implicated in this outbreak, E. coli O157:H7, causes about 74,000 infections in the U.S. each year, leading to more than 2,000 hospitalizations and 61 deaths. Infections are especially dangerous for children younger than 5 and can cause acute kidney failure.