McDonald's has stopped selling Quarter Pounder burgers at one-fifth of its outlets across the U.S. following an E. Coli outbreak linked to the burgers in 10 states. The fast-food chain removed the item from its menu in states including Colorado, Kansas, Utah, Wyoming, and parts of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, and Oklahoma, as reported by the Associated Press.

This action follows the death of one individual and numerous E. Coli infections, which the U.S. Centers for Disease Control and Prevention (CDC) connected to Quarter Pounders. McDonald's U.S. Chief, Joe Erlinger, stated on NBC’s Today show that the company acted swiftly to pull the burger from locations affected by the outbreak.

"Our main focus is to restore trust among American consumers after recent events," Erlinger said, adding that the contaminated product likely passed through the company's supply chain.

CDC spokesman Tom Skinner, quoted by Reuters, said the agency expects to see additional E. Coli cases, but praised McDonald's for taking quick preventive measures.

When asked why McDonald's didn’t shut down any locations, the company explained that the investigation by health authorities didn’t point to issues with its food preparation practices.

Preliminary findings from the U.S. Food and Drug Administration (FDA) suggest that fresh, raw slivered onions, a key ingredient in the Quarter Pounder, may be responsible for the contamination. Although raw onions are also used in some of McDonald’s breakfast sandwiches, those items are not sold at the affected outlets. Other burgers, such as the Big Mac, use diced, cooked onions instead.

McDonald’s said it has been working with federal food safety regulators since last week, when the potential E. Coli link was first identified. However, the widespread popularity of the Quarter Pounder and the scope of the problem have made it difficult to pinpoint the exact source of the contamination.

The fast-food giant, which operates more than 14,000 locations across the U.S., serves over a million Quarter Pounder burgers every two weeks in the states impacted by the outbreak. The company is also looking to find a new regional supplier for fresh onions.