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The General Mills cereal Honey Nut Cheerios is seen Sept. 23, 2014, in this photo illustration. The company wrote Monday that it was "embarrassed" to have to recall the cereal. Getty Images

General Mills announced Monday a voluntary recall on certain types of Cheerios the company said were contaminated with gluten at its production facility in Lodi, California. Boxes of Original Cheerios and Honey Nut Cheerios made there for about two weeks this past July could contain wheat flour in addition to oat flour, even though the cereal was announced this summer to be gluten-free, according to a news release. CNBC reported that about 1.8 million boxes were affected.

The company wrote that it was "embarrassed" to have to recall the cereal. "We want to reassure that this was an isolated incident, and we have implemented a solution to ensure that this will not happen again," it said in the release. "We care about what you and your family eat, and we are truly sorry for this mistake."

General Mills announced in February its plan, starting in July, to make gluten-free five Cheerios cereals: Original Cheerios, Honey Nut Cheerios, Multi-Grain Cheerios, Apple Cinnamon Cheerios and Frosted Cheerios. Initially celebrated by people with celiac disease or gluten sensitivities, the news turned controversial due to limitations in Food and Drug Administration policies.

FDA rules allow foods to be advertised as gluten-free if they don't have any gluten grains in them, but companies aren't forced to check their final products for cross-contamination, according to U.S. News and World Report. Advocates have also argued that the FDA hasn't set its bar high enough in terms of the "unavoidable" gluten presence that's allowed -- 20 parts per million.

Gluten-Free Living reported last month that 39 people had submitted complaints to the FDA claiming they got sick after eating Cheerios advertised as being gluten-free. General Mills' testing involves combining cereals from several different boxes, which bloggers like Gluten Free Watchdog said can achieve the 20 parts per million measurement even if a few boxes have extremely high gluten content.

For questions about the recall, contact General Mills at 800-775-8370.