Chipotle Mexican Grill plans to reopen all 43 restaurants previously shut down in Oregon and Washington after an Escherichia coli (E. coli) outbreak occurred last month. Hundreds of E. coli tests have come back negative, so no exact source of the outbreak has been determined as of yet.

Forty-two people--15 in Oregon and 27 in Washington--have reportedly become ill after eating at one of the now closed restaurants. Although only 11 of those restaurants have been linked to the outbreak, Chipotle decided to close all locations in the Pacific Northwest region as a precaution on October 31. At least one foodborne illness victim has filed a lawsuit.

The fast food chain says it has replaced all ingredients in the affected restaurants, and they believe that consumers will not be at risk by returning to Chipotle. It has been reported that authorities do believe that fresh produce could be the culprit in the E. coli outbreak, but testing has not proven that theory yet. It is possible that the contaminated food may have been consumed or thrown out before samples could be collected. The stores have tested fresh produce, raw meat and dairy products prior to restocking. Surfaces and equipment were also swabbed for the presence of E. coli. The stores have undergone a round of sanitizing and will be implementing more safety procedures and audits at all of its locations nationwide.

"The safety of our customers and integrity of our food supply has always been our highest priority," Steve Ells, chairman and co-CEO of Chipotle, said in a statement. "If there are any opportunities for us to do better in any facet of our sourcing or food handling -- from the farms to our restaurants -- we will find them. We are sorry to those affected by this situation, and it is our greatest priority to ensure that we go above and beyond to make certain that we find any opportunity to do better in any area of food safety."

Chipotle has said the Oregon and Washington restaurants will open “in the coming days.”

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