The number of cases in a deadly E. coli outbreak linked to McDonald's Quarter Pounders has risen to 75, according to new federal data released Friday.
Cases have been reported in 13 states, according to the Centers for Disease Control and Prevention (CDC).
Most of the cases have been in Colorado, which has 26 reported cases, and Montana, which has 13 reported cases, according to the CDC.
MORE: Onions recalled by McDonald's supplier as officials expect E. coli outbreak cases to riseCases have also been reported in Iowa, Kansas, Michigan, Missouri, Nebraska, New Mexico, Oregon, Utah, Washington, Wisconsin and Wyoming, according to the CDC, which further notes that illnesses have occurred between Sept. 27 and Oct. 10 of this year.
Of the 61 people about whom the CDC has information, 22 have been hospitalized, and two developed hemolytic uremic syndrome, a serious, potentially fatal complication of E. coli infection that can cause kidney failure, according to the CDC.
One death has been reported in Colorado in connection with the outbreak. The person was a resident of Mesa County in the western part of the state, according to the Mesa County department of health.
"The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses," the CDC said in its update. "This is because many people recover without medical care and are not tested for E. coli. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak."
McDonald's says either fresh, slivered onions or beef patties used for the Quarter Pounder may be behind the outbreak.
MORE: What to know about the listeria outbreak that has left 57 sick, 9 deadFollowing the initial announcement of the outbreak on Tuesday, the fast-food company announced it had proactively removed two ingredients from stores across two affected regions. The company's leadership team said that a majority of other menu items are not impacted, according to the CDC investigation.
McDonald's confirmed in a statement to ABC News that Taylor Farms is the supplier of the sliced onions the fast-food chain removed. The U.S. Food and Drug Administration (FDA) is investigating but has not definitively stated the source of the E. coli, although they have said that the onions are a “likely source of contamination.”
In an updated statement on Friday, McDonald's said slivered onions from a Taylor Farms facility in Colorado Springs were distributed to roughly 900 McDonald’s restaurants, in Colorado, Kansas, Wyoming and portions of other states. Some were in airports "which may account for illnesses in other states," McDonald's said.
"Nothing is more important to us than the quality and safety of our food, which is why McDonald’s took swift and decisive action to protect the health of our customers," the fast-food company said in the updated statement.
McDonald's said it removed all slivered onions from the Taylor Farms facility from its restaurants as of Oct. 22, but "due to broad concern and our unwavering commitment to food safety we have made the decision to stop sourcing onions from Taylor Farms’ Colorado Springs facility indefinitely."
Taylor Farms issued a voluntary recall on Wednesday for its raw onions.
ABC News' Kelly McCarthy and Taylor Dunn contributed to this report.