McDonald’s Quarter Pounder Beef Patties Are Not the Source of E. Coli Outbreak, Company Says

No E. coli was found in samples of beef patties used in McDonald’s Quarter Pounders that were linked to a deadly outbreak, a company spokesperson said Sunday, citing Colorado Agriculture Department testing.

The department has no further plans to test the beef patties, the company spokesperson said, and the patties have been ruled out as a source of the outbreak.

The most likely source of contamination was chopped onions from a single source, the company spokesman said, citing the Food and Drug Administration.

McDonald’s indefinitely stopped sourcing cut onions from that source — Taylor Farms Colorado Springs — on Sunday, the company spokesman said, days after it removed Taylor Farms onions from its supply chain.

Taylor Farms onions were sold at stores in Colorado, Kansas, Wyoming and parts of other nearby states, the spokesperson said. Some of those locations include airports, which could explain cases in other states.

McDonald’s spokesperson said the company is confident that beef suppliers will be asked for a new supply of patties for distribution. Quarter Pounders are expected to be available in restaurants this week.

All 900 restaurants that source onions from Taylor Farms Colorado Springs will continue to sell Quarter Pounders without onions for the time being, the company spokesperson said.

No other McDonald’s burgers or menu items have been affected by the outbreak.

The strain of E. coli in the outbreakcalled O157:H7, produces a powerful toxin that can damage the lining of the small intestine.

The The outbreak was first reported on TuesdayWhen the Centers for Disease Control and Prevention announced it was investigating an E. coli outbreak linked to McDonald’s Quarter Pounders in multiple states, prompting the fast-food chain to stop using sliced ​​onions and quarter pounds in several states beef patties, the agency said at the time.

The CDC said Tuesday that the first E. coli case linked to McDonald’s occurred on September 27. State health officials in Colorado notified the CDC on October 10 of an unusual increase in the disease, and the agency began an investigation on October 15, Matt Wise, chief of the CDC’s Outbreak Response and Prevention Branch, told NBC News.

The CDC focused his research on the chopped onions at the Quarter Pounders by Wednesday. On Thursday, McDonald’s said the onions linked to the outbreak came from Taylor Farms.

On Wednesday, distributor US Foods said Taylor Farms is recalling four raw onion products out of an abundance of caution due to “potential E. coli contamination.” The company urged its customers, including restaurants, to stop using it and destroy affected products as soon as possible.

It also prompted other restaurant chains in Colorado – including Illegal Pete’s and Taco Bell – to stop using onions on their menus.

A spokesperson for Yum! Brands, the parent company of Taco Bell, said select Pizza Hut and KFC locations have also removed fresh onions from their menus. There are no signs of E. coli illnesses associated with these restaurants.

The FDA said Thursday it is investigating Taylor Farms as the possible source of the E. coli outbreak linked to the Quarter Pounders, but added that “we are looking at all possible sources.”

A spokesperson for Taylor Farms did not immediately respond to a request for comment on Sunday.

As of Friday, 75 people in 13 states had been infected with the E. coli strain and one person had died, according to the CDC.

Twenty-two people have been hospitalized, and two people have developed hemolytic uremic syndrome, a serious complication that can cause permanent kidney failure or death.

Several people McDonald’s sued claim they have become ill after eating at the restaurant.

This article was originally published on NBCNews.com