Testing has ruled out beef patties as the source of the outbreak of E. coli poisoning tied to McDonald's Quarter Pounders, the company said Sunday. It will resume selling the Quarter Pounder in the coming week.

The U.S. Food and Drug Administration (FDA) continues to believe that slivered onions from a single supplier are the likely source of contamination, McDonald's said.

As of Friday, the outbreak had expanded to at least 75 people sick in 13 states, federal health officials said. A total of 22 people have now been hospitalized, and two have developed a dangerous kidney disease complication, the Centers for Disease Control and Prevention (CDC) said. One person has died in Colorado.

Early information analyzed by the FDA showed that uncooked slivered onions used on the burgers "are a likely source of contamination," the agency said. McDonald's has confirmed that Taylor Farms, a California-based produce company, was the supplier of the fresh onions used in the restaurants involved in the outbreak and that they had come from a facility in Colorado Springs, Colo.

The 900 McDonald's restaurants that normally received slivered onions from Taylor Farms' Colorado Springs facility will resume sales of Quarter Pounders without slivered onions, McDonald's said.

Taylor Farms said Friday it had pre-emptively recalled yellow onions sent to its customers from its Colorado facility and continues to work with the CDC and the FDA as they investigate.

The outbreak involves infections with E. coli 0157:H7, a type of bacteria that produces a dangerous toxin. It causes about 74,000 infections in the United States annually, leading to more than 2,000 hospitalizations and 61 deaths each year, according to the CDC.

A spokesperson for McDonald's Canada said the E. coli concern does not extend to the fast-food giant's Canadian locations.