The US food safety watchdog is believed to have received at least 125 complaints from people who claim to have developed gastrointestinal problems after consumption of gluten-free Cheerios.
Earlier this week, General Mills recalled 1.8 million boxes of gluten-free Cheerios and gluten-free Honey Nut Cheerios after it was found that these products contained wheat, while Cheerios are made primarily from oats.
The recalled products were manufactured in July at its Lodi facility in California.
While the Cheerios recall involved four days of production, the Honey Nut Cheerios recall covered 13 days.
General Mills cereal division president Jim Murphy has stated that the company was "embarrassed and truly sorry" about the recall.
Explaining the problem, Murphy said: "Our Lodi production facility lost rail service for a time and our gluten-free oat flour was being off-loaded from rail cars to trucks for delivery to our facility on the dates in question.
"In an isolated incident involving purely human error, wheat flour was inadvertently introduced into our gluten-free oat flour system at Lodi. That error resulted in an undeclared allergen, wheat, being present in products labeled as gluten free at levels above the FDA gluten-free standard."
General Mills has begun testing completed products, and included flour-handling protocols at all its facilities in order to avoid such problems from occurring again.
"We sincerely apologise to the gluten-free community and to anyone who may have been impacted. We care deeply about making safe, nutritious, gluten free products more widely available, and we've worked very hard to ensure our products are gluten free. Today we must acknowledge that we failed to meet that commitment for a time, and we're recalling all affected products as a result," he added.
The FDA stated that they did not receive reports of anyone being hospitalised, or of any deaths due to consumption of the recalled products.
The agency had conducted lab tests, which indicated 43 parts per million (ppm) of gluten in one sample of Honey Nut Cheerios. However, for a product to be considered as gluten-free, it must contain less than 20ppm of gluten.
