A deadly outbreak of E. coli poisoning tied to McDonald’s Quarter Pounders has expanded, with at least 75 people sick in 13 states, federal health officials said Friday.

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 said. One person has died in Colorado.

No definitive source of the outbreak has been identified, officials with the U.S. Food and Drug Administration said. 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, Colorado.

“We have made the decision to stop sourcing onions from Taylor Farms’ Colorado Springs facility indefinitely,” McDonald’s said in a statement released late Friday.

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

“It saddens us to see the illnesses and affected individuals and families,” from the outbreak, the family-owned company said.

McDonald’s pulled the Quarter Pounder burger from menus in several states — mostly in the Midwest and Mountain states — when the outbreak was announced Tuesday. McDonald’s said Friday that slivered onions from the Colorado Springs facility were distributed to approximately 900 of its restaurants, including some in transportation hubs like airports.

The new cases reported Friday were a sharp increase from the original tally of 49 in 10 states. Most illnesses were reported in Colorado, with 26 cases. At least 13 people were sickened in Montana, 11 in Nebraska, 5 each in New Mexico and Utah, 4 each in Missouri and Wyoming, two in Michigan and one each in Iowa, Kansas, Oregon, Wisconsin and Washington, the CDC reported.

McDonald’s said Friday it didn’t pull the Quarter Pounder from any additional restaurants due to the increase in the CDC’s illness count. The company noted that some cases in states outside the original region were tied to travel.

The CDC said some people who got sick reported traveling to other states before their symptoms started. At least three people said they ate at McDonald’s during their travel. Illnesses were reported between Sept. 27 and Oct. 11.

Taylor Farms notified its customers directly about the onion recall but did not tell the public about it, an FDA official said. Companies often issue press releases and the FDA sends public notifications for recalls, but they are not required.

While it remains unclear if the recalled onions were the source of the outbreak, several other fast-food restaurants — including Taco Bell, Pizza Hut, KFC and Burger King — pulled onions from some menus in certain areas this week.

Restaurant Brands International, which owns Burger King, said that 5% of its restaurants use whole onions distributed by Taylor Farms’ Colorado facility. They are washed, peeled and sliced by employees.

Even though it wasn’t contacted by health officials and it had no indications of illness, Restaurant Brands said it asked the restaurants that received onions from the Colorado facility to get rid of them.

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 U.S. annually, leading to more than 2,000 hospitalizations and 61 deaths each year, according to CDC.

People sickened in the outbreak have already moved to sue McDonald’s, according to court records. According to her lawsuit, Clarissa DeBock ate food from a local McDonald’s in Nebraska on Sept. 18, fell ill on Sept. 23 and sought emergency care two days later before she was diagnosed with an E. coli infection.

Symptoms of E. coli poisoning can occur quickly, within a day or two of eating contaminated food. They typically include fever, vomiting, diarrhea or bloody diarrhea and signs of dehydration — little or no peeing, increased thirst and dizziness. The infection is especially dangerous for children younger than 5, people who are elderly, pregnant or who have weakened immune systems.

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AP business reporter Dee-Ann Durbin contributed reporting from Detroit.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.