McDonald's CEO Chris Kempczinski apologized to customers on Tuesday after an outbreak of E. coli that has sickened dozens and left one dead was linked to its Quarter Pounder hamburgers.

"On behalf of the entire system, we are sorry for what our customers have experienced," Kempczinski said during the company's earnings call. "We offer our sincere and deepest sympathies, and we are committed to making this right."

"Hearing reports of how this has impacted our customers has been wrenching for us," Kempczinski added. 

As of Oct. 25, the outbreak has resulted in 75 cases across 13 states, according to the Center for Disease and Control's latest figures. There have been 22 hospitalizations and one death.

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The last serious public health issue in the U.S. associated with McDonald's was more than 40 years ago, according to Kempczinski.

After the CDC informed the company of the outbreak, McDonald's removed beef and onions from its supply chain, and Taylor Farms issued a recall of yellow onions.

The Food and Drug Administration (FDA) is in the midst of investigating whether Taylor Farms, which supplied the slivered onions to McDonald's in the areas where the E. coli outbreak occurred, is the source of the contamination. 

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McDonald's said it has stopped sourcing onions from this facility indefinitely. 

Using CDC epidemiological data and McDonald's supply chain traceback data, beef was ruled out as the source of the outbreak. The company has told its beef suppliers to resume making the fresh patties and expects Quarter Pounders to be available again at all stores over the coming week. 

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However, slivered onions will still not yet be available as a topping in the locations impacted by the outbreak. 

FOX Business' Breck Dumas contributed to this report.