EXPLAINER: What we know about shuttered baby formula plant

WASHINGTON (AP) — At the center of the nationwide baby formula shortage is a single factory: Abbott Nutrition's plant that has been closed for more than three months because of contamination problems.

On Monday, U.S. officials announced a deal with Abbott that paves the way to restart production at the Sturgis, Michigan, facility, the largest in the U.S. and source of leading brands like Similac.

But it's not yet clear how soon the site will be up and running. And even bigger questions remain unanswered, including what caused the contamination and whether U.S. regulators could have alleviated the current formula shortage by stepping in sooner. The plant shutdown exacerbated ongoing supply chain problems among U.S. formula makers.

WHAT CAUSED THE SHUTDOWN?

In mid-February, Abbott announced it was recalling various lots of three powdered infant formulas from the plant, after federal officials began investigating rare bacterial infections in four babies who were fed formula. Two of the infants died. But it's not certain the bacteria came from the plant; strains found at the plant didn't match the two available samples from the babies.

The company halted production while Food and Drug Administration inspectors conducted a six-week investigation of the plant.

A preliminary report released in March found traces of a bacteria — cronobacter— on several surfaces throughout the plant, though not in areas used to make the powder. Plant records showed Abbott had detected the bacteria eight times in its products or facility since 2019.

Inspectors also flagged other problems, including standing water on the floor and employees who didn't properly sanitize their hands.

WHAT IS CRONOBACTER?

The bacteria occurs naturally in soil, water and other parts of the environment. Infections...