McDonald's Quarter Pounder burgers to return to restaurants affected by E. coli outbreak

McDonald's Quarter Pounder burgers will return to roughly 900 restaurants this week after the fast-food giant pulled the menu item linked to a deadly E. coli outbreak.

Affected restaurants — roughly a fifth of the company's U.S. footprint — will be serving the Quarter Pounder burgers without slivered onions for the foreseeable future as health authorities continue their investigation into the source of the outbreak. That change will affect restaurants in Colorado, Kansas and Wyoming and portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma and Utah.

"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," Cesar Pina, chief supply chain officer for McDonald's North American operations, said in a letter sent to the company's U.S. system.

The Colorado Department of Agriculture's testing did not detect E. coli in samples of the beef patties taken from restaurants in the area, according to Pina. The agency isn't planning further tests of the company's beef.

Instead, health authorities have honed in on slivered onions used in the Quarter Pounders as the likely suspect for the outbreak. The Food and Drug Administration is still investigating if onions produced by Taylor Farms are responsible. McDonald's has stopped using Taylor Farms as a supplier for the ingredient indefinitely.

McDonald's is now asking its beef suppliers to produce a new supply of the fresh beef patties used in its Quarter Pounders, Pina wrote in a letter sent to the company's U.S. system. Customers can expect to see the menu item back in all