McDonald’s says they believe slivered onions supplied from a California-based produce company have been isolated as the likely cause of the E. Coli outbreak tied to the company’s Quarter Pounders.

Early information analyzed by the FDA showed that uncooked slivered onions used on the burgers “are a likely source of contamination,” the agency said.

The company says the onions were distributed from Taylor Farms’ Colorado Springs facility and historically 900 restaurants have received onion supplies from Taylor Farms.

The 900 restaurants that have historically received onions from Taylor Farms are in states which include Colorado, Kansas, and Wyoming, as well as portions of Idaho, Iowa, Missouri, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Utah. Texas is not included in the list.

“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,” said McDonald’s North America Chief Supply Chain Officer Cesar Piña.

McDonald’s said testing was done over the weekend by the Colorado Department of Agriculture which did not detect E. Coli in samples taken of Quarter Pounder beef patties from restaurants in the area.

“Overlaying the CDC’s Epidemiological data with our Supply Chain traceback data, we have ruled out Quarter Pounder patties as the source,” Piña said. “Last week, out of an abundance of caution, we stopped distributing Quarter Pounder beef patties to the impacted area. Based on the above information, we are now confident in asking our beef suppliers to produce a new supply of fresh beef patties for the impacted areas. We will resume distribution of that fresh supply and the Quarter Pounder is expected to be available in all restaurants in the coming week.”

Piña says the 900 restaurants that received slivered onions in the affected area will start selling Quarter Pounders again, just without the onions.

“The FDA is continuing its investigation into Taylor Farms’ Colorado Springs facility. As a reminder, McDonald’s removed slivered onions from this facility from our supply chain on October 22 and shared that we had decided to stop sourcing onions from Taylor Farms’ Colorado Springs facility indefinitely. Over the past few days, you’ve likely seen that additional food service providers and restaurant brands that received onions from this facility have moved to stop selling and/or recall onions,” Piña said.

McDonald’s President Joe Erlinger thanked employees, governmental agencies, and franchisees and restaurant teams for helping to find and contain the issue.

“Because of your work, this issue was quickly identified and contained. Because of your work, our customers can be confident that any contaminated product related to this outbreak has been removed from our supply chain. Because of your work, we can confidently say that it’s safe to eat at McDonald’s restaurants. To all: I hope our actions and today’s steps demonstrate McDonald’s continued commitment to food safety and the strong partnership that we cherish having with each of you,” Erlinger said in a video message.

On Friday, federal officials said at least 75 people had been sickened from the outbreak. One person in Colorado died.