PORTLAND, Ore. (KATU) — The Centers for Disease Control and Prevention is investigating an E.Coli outbreak linked to McDonald’s Quarter Pounder hamburgers.

According to official information, almost 50 people in 10 states have become ill, and one case has been reported in Oregon. Multnomah County Health officials confirmed the individual case did not occur in the Portland metropolitan area.

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While the investigation is ongoing, McDonald’s has already begun withdrawing menu items from some locations. According to the Food and Drug Administration, both chopped onions and beef patties on the Quarter Pounder could be the cause. The CDC notes that the Quarter Pound beef patties are only used for the Quarter Pounders.

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“We urge people who become ill after eating a Quarter Pounder at McDonald’s in the last month to report it to their doctor,” a spokesperson for the Multnomah County Health Department told KATU.

“People infected with the E. coli O157:H7 strain typically experience severe stomach cramps, bloody diarrhea and vomiting, and fever within three to four days of ingesting the bacteria. Most people recover within seven days without the need for treatment. However, complications may require hospitalization.”