Flour is one of the most basic ingredients in baking, but federal health investigators are advising residents in the United States to steer clear of it.

Why? The product is currently in close scrutiny because it has reportedly been contaminated with a potentially deadly microbe that is often found in animal feces, investigators say.

Indeed, in early June, American food company General Mills announced the recall of approximately 10 million pounds of flour amid suspicion of E.coli contamination.

One month later, the U.S. Food and Drug Administration (FDA) warned customers not to swipe a bite of dough or lick batter from a bowl because it may cause infection.

As of July 31, about 46 people in 21 states have been sickened by the E.coli-tainted flour, with 45 million pounds of it expected to be recalled, officials report.

How Did The Fecal Bacteria Get Into The Flour?

The question that consumers are wondering about is this: in the first place, how did the bacteria get into the flour?

According to the FDA, the batches of flour that sickened residents were made between November 2015 and February 2016.

All of the contaminated flour was produced by a single factory located in Kansas City, Missouri, the agency says.

In the past few years, the Centers for Disease Control and Prevention (CDC) has investigated countless multi-state E.coli outbreaks linked to sprouts, but there has never been widespread multi-state outbreaks linked to flour until now.

The FDA traced the recent cases of infection and found that it was linked to the contaminated General Mills product. So far, health officials have discovered two different E.coli strains which produce a toxin that makes people ill.

Both the CDC and the FDA are actively examining how the dangerous E.coli bacteria got into the flour, although both agencies have yet to determine the source of the contamination.

The E.coli microbe typically lives in animal intestines and is most commonly spread through fecal contamination.

On the other hand, flour is developed from wheat that grows in open fields. It is a raw agricultural product because no treatment procedure kills contaminants such as bacteria before the product reaches the market.

Dr. Karen Neil, an epidemiologist at the CDC, says as a result of the lack of treatment, there is a possibility for contamination between the field and the packaging.

Additionally, experts say poor hygiene and unwashed hands may contribute to the spread of the bacteria. However, it is still unknown whether or not improper hand washing may have been one of the main triggers of the contamination.

What Are The Symptoms Of E.coli Infection?

The E.coli strains detected by the FDA can cause abdominal cramps, vomiting and diarrhea. In some of the cases, the infected individuals get better in a week even without being treated.

However, in extreme cases, infected patients can experience more intense symptoms such as kidney failure, and may even lead to death, experts say.

The CDC reported that 13 people impacted by the E.coli contamination required to be hospitalized, while one suffered kidney failure.

Which Products Were Recalled?

Officials say the recall is a small fraction of the 2.5 billion pounds of flour produced by General Mills every year.

The following unbleached, all-purpose and self-rising batches of flour were recalled: varieties from Gold Medal, General Mills, Signature Kitchens and Wondra flour brands. Several cake mixes, a pancake mix and a biscuit mix from General Mills were also withdrawn.

Meanwhile, a statement from General Mills says the company does not believe that the facility in Kansas City is the main source of the contamination. Still, the company has increased cleaning protocols out of caution.

"Only a small sub-set of flour produced at the Kansas City plant has been traced back to individuals who have become ill," General Mills tells The Associated Press. "To date, E. coli has not been found in testing of the manufacturing facility."

Photo: Rebecca Siegel | Flickr