The outbreak, which was first reported Oct. 22, sickened at least 104 people in 14 states, including 34 who were hospitalized, according to the U.S. Food and Drug Administration. One person in Colorado died and four people developed a potentially life-threatening kidney disease complication.

The FDA, which conducted the investigation along with the U.S. Centers for Disease Control and Prevention and state health departments, linked the outbreak to yellow onions distributed by California-based Taylor Farms and served raw on Quarter Pounders at McDonald’s restaurants in Colorado, Kansas, Wyoming and other states.

There have been no new cases reported since Oct. 21, when McDonald’s pulled the Quarter Pounder off its menu in the affected states, the CDC said Tuesday. Taylor Farms initiated a voluntary recall of yellow onions on Oct. 22.

Federal and state health officials in Colorado didn’t find the strain of E. coli that caused the illnesses in onions it tested or in any samples from the environment. But they concluded that evidence showed that recalled yellow onions were the likely source of the outbreak.

“McDonald’s is no longer serving recalled onions and there does not appear to be a continued food safety concern related to this outbreak,” the FDA said Tuesday in a statement.

McDonald’s briefly pulled Quarter Pounders from 3,000 U.S. stores as a result of the outbreak, then narrowed that to 900 stores once testing had pinpointed onions — and not hamburger patties — as the likely source of E. coli. The company found an alternate supplier and resumed selling Quarter Pounders with slivered onions at all U.S. stores last month.

But the outbreak has hurt demand. In mid-November, McDonald’s said it planned to spend $100 million to bring customers back to stores, including $65 million that will go directly to the hardest-hit franchisees.

Chicago-based McDonald’s wouldn’t say Tuesday whether its sales have returned to normal levels in the affected regions. But it thanked U.S. regulators for their quick action and said it remains confident in its rigorous food-safety standards.

McDonald’s last major food-safety issue happened in 2018, when more than 500 people contracted an intestinal illness after eating its salads.

McDonald’s also declined to comment Tuesday on legal action against the company as a result of the E. coli outbreak.

Nicole and Richard West of Townsend, Montana, are suing McDonald’s after their 11-month-old daughter, Logan, was hospitalized in October with E. coli poisoning. The toddler ate a few bites of her father’s Quarter Pounder hamburger with onions during a family road trip on Oct. 2.

She fell ill a few days later with severe vomiting and diarrhea. Her mother rushed her to the hospital, where she was found to be infected with E. coli O157:H7, which can cause life-threatening illness, particularly in young children.

Richard West also fell ill but didn’t seek medical attention because he was at home caring for the family’s other children. He lost more than two weeks of work as a truck driver because of the outbreak and the family faces a barrage of medical expenses.

Nicole West said Tuesday that Logan’s health has improved but the outbreak has shaken the family’s confidence in the fast-food giant.

“With kids, when you want to go out to eat, they want to go to McDonald’s. They want to get a Happy Meal,” West said. “But we just don’t trust it anymore.”