Los Angeles — McDonald’s announced Sunday that Quarter Pounders will again be on its menu at hundreds of its restaurants after testing ruled out beef patties as the source of the outbreak of E. coli poisoning tied to the popular burgers that killed one person and sickened at least 75 others across 13 states.

The U.S. Food and Drug Administration continues to believe that slivered onions from a single supplier are the likely source of contamination, McDonald’s said in a statement. It said it will resume selling the Quarter Pounder at affected restaurants — without slivered onions – in the coming week.

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 had been hospitalized, and two developed a dangerous kidney disease complication, the Centers for Disease Control and Prevention said. One person 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, Colorado.

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

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.

Testing by the Colorado Department of Agriculture ruled out beef patties as the source of the outbreak, McDonald’s said.

The department of agriculture received multiple lots of fresh and frozen beef patties collected from various Colorado McDonald’s locations associated with the E. coli investigation. All samples were found to be negative for E. coli, the department said.

Taylor Farms said Friday that 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.

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.

Colorado had the most illnesses reported as of Friday, 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 and 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.

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.

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 and people who are elderly, pregnant or who have weakened immune systems. 

Colorado has seemingly eliminated one ingredient as a cause for death and illness, as states continue to investigate the source of an E. coli outbreak involving the Quarter Pounder hamburger at dozens of McDonald’s locations. As a result, the Quarter Pounder will begin to return to certain locations.

The Colorado Department of Agriculture announced McDonald’s brand “fresh and frozen beef patties” tested negative for E. coli after its lab analyzed dozens of subsamples.

CDA says it has completed all beef testing and does not anticipate receiving further samples.

Meanwhile, the federal investigation into the deadly E. coli outbreak in Colorado has focused on ground beef patties and onions. There continues to be no evidence that onions grown in Colorado are linked to the outbreak.

According to McDonald’s, The 900 restaurants that historically received slivered onions from Taylor Farms’ Colorado Springs facility will resume sales of Quarter Pounders without slivered onions. Those restaurants are in Colorado, Kansas, and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma and Utah. The restaurant chain also noted it has stopped getting onions from that facility indefinitely.

“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 North American Chief Supply Chain Officer Cesar Piña said in a statement Sunday

Since the outbreak was first announced, CBS News Colorado confirmed one older man on the Western Slope died after consuming a Quarter Pounder from a McDonald’s location in the state. Initial information also confirmed more than two dozen people had become ill due to E. coli-affected Quarter Pounders.

Nationwide, this outbreak has sickened 75 people in more than a dozen states, but Colorado remains the only state impacted that has experienced a death due to it. 

The Colorado Department of Public Health says there have been 26 cases reported in nine different Colorado counties, and they are located in several different parts of the state:

• Arapahoe County
• Chaffee County
• El Paso County
• Gunnison County
• Larimer County
• Mesa County
• Routt County
• Teller County
• Weld County

The illnesses were reported between the last days of September and through Oct. 11. An investigation by the Centers for Disease Control and Prevention into the outbreak is ongoing.

McDonald’s company leaders previously said they’ve taken Quarter Pounders off the menu in states where there have been outbreaks.