McDonald’s announced Sunday that Quarter Pounders will be back on the menus of hundreds of restaurants after testing excluded beef patties. Source of E Coli poisoning It has been linked to the popular burgers, which have killed one person and sickened at least 75 in 13 states.

In a statement from McDonald’s, it was stated that the US Food and Drug Administration continues to believe that chopped onions from a single supplier are a possible source of contamination. The Quarter Pounder will continue to be sold without sliced ​​onions at affected restaurants next week, he said.

As of Friday, the outbreak had spread to at least 75 people in 13 states, federal health officials said. A total of 22 people were hospitalized, and two developed a dangerous complication of kidney disease, the Centers for Disease Control and Prevention said. One person died in Colorado.

Initial information analyzed by the FDA showed that uncooked sliced ​​onions used in the burgers were a “possible source of contamination.” McDonald’s confirmed that Taylor Farms, a California-based produce company, was the supplier of the scallions used at restaurants involved in the outbreak and that they came from a facility in Colorado Springs, Colorado.

When the outbreak was announced Tuesday, McDonald’s removed its Quarter Pounder burger from menus in several states, mostly in the Midwest and Mountain states. McDonald’s said Friday that slivers of onions from its Colorado Springs facility were distributed to about 900 of its restaurants, including some at transportation hubs such as airports.

The company said it removed sliver onions from that facility from its supply chain on Tuesday. McDonald’s said it has decided to “indefinitely” stop supplying onions from Taylor Farms’ Colorado Springs facility.

McDonald’s said the 900 McDonald’s restaurants that normally buy slivered onions from Taylor Farms’ Colorado Springs facility will continue selling Quarter Pounders without slivered onions.

McDonald’s stated that the source of the outbreak was not beef patties in tests conducted by the Colorado Department of Agriculture.

The agriculture department received a large number of fresh and frozen beef patties collected from several Colorado McDonald’s locations connected to the E Coli investigation. The ministry said all samples were found negative for E Coli.

Taylor Farms said Friday that it is preemptively recalling yellow onions shipped to customers from its Colorado facility and continues to work with the CDC and FDA during the investigation.

While it remains unclear whether the recalled onions were the source of the outbreak, some other fast food restaurants, including Taco Bell, Pizza Hut, KFC and Burger King, removed the onions from some menus in certain regions this week.

Colorado was the state with the highest number of cases reported, with 26 cases as of Friday. At least 13 in Montana, 11 in Nebraska, five each in New Mexico and Utah, four in Missouri and Wyoming, two in Michigan, Iowa, Kansas, Oregon, Wisconsin and Washington, the CDC reported. one person each fell ill.

McDonald’s said in a statement Friday that it was not withdrawing the Quarter Pounder from any additional restaurants and noted that some cases in states outside the original region were linked to travel.

The CDC said some people who got sick reported traveling to other states before their symptoms began. At least three people said they ate at McDonald’s during their travels. The illnesses were reported between September 27 and October 11.

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

Symptoms of E. coli poisoning can appear rapidly within a day or two after consuming contaminated food. It typically includes fever, vomiting, diarrhea or bloody diarrhea, and signs of dehydration (little or no urination, increased thirst, and dizziness). The infection is especially dangerous for children under 5 years of age, the elderly, pregnant women, or people with weakened immune systems.