Quarter Pounders will soon be back on the menu at McDonald’s restaurants nationwide after its beef patties were ruled out as the source of an E. coli outbreak in several states.

Last week, the Centers for Disease Control and Prevention issued a food safety alert about an investigation into possible E. coli contamination linked to its Quarter Pounder burgers, as reported by The Dallas Express. At the time, investigators were working to determine if the beef patties or slivered onions on the hamburger were the likely source of the contamination.

On Sunday, McDonald’s announced that its beef patties had been ruled out as the source. The fast food chain will resume selling its Quarter Pounders but without the slivered onions.

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Federal health officials have focused on raw slivered onions from a particular supplier as the likely source of the contamination.

“The issue appears to be contained to a particular ingredient and geography, and we remain very confident that any contaminated product related to this outbreak has been removed from our supply chain and is out of all McDonald’s restaurants,” McDonald’s said in the statement, adding that it “had decided to stop sourcing onions from Taylor Farms’ Colorado Springs facility indefinitely.”

Taylor Farms, a Colorado-based supplier of fresh onion products, issued a voluntary recall last week. Other fast food restaurants, including Burger King, Taco Bell, KFC, and Pizza Hut, which use this supplier for some of their franchises, have also removed onions from their menus.

According to the most recent update from the U.S. Food & Drug Administration, the E. coli outbreak linked to Quarter Pounders has affected consumers in 13 states, with 75 persons reportedly sickened and 22 hospitalized. Two people developed hemolytic uremic syndrome, a serious condition that can cause kidney failure, and one person died.