During their five-day inspection, inspectors noted a handful of food safety issues, but officials didn’t find any problems serious enough to warrant administrative or regulatory action — and they didn’t find evidence of Cronobacter sakazakii, a rare bacteria that can cause deadly infections in infants, according to inspection documents released by the agency.

The day the inspection began, however, the FDA received a report of a Minnesota infant who was hospitalized with Cronobacter sakazakii after having consumed formula that had been produced in the plant, according to the Minnesota Department of Health. It was the first of four complaints the agency would receive in the coming months about formula produced in this particular plant: Four infants were hospitalized. Two died.

The complaints prompted FDA inspectors to go back into the plant in late January after a nearly four-month delay that the agency has declined to explain. When they did, they found no fewer than five different strains of Cronobacter on plant equipment that could come in contact with formula — on the floors, on a wall and on a door, according to inspection documents.

Consumer advocates and other outside experts said the failure to uncover more serious food safety problems, or to detect the deadly bacteria last fall, raises serious questions about the effectiveness of the agency’s inspections.

“One of the lessons from this seems to be that FDA’s formula inspections could be a lot more rigorous,” said Sarah Sorcher, deputy director of regulatory affairs at the Center for Science in the Public Interest. “It’s clear that FDA caught a lot of things in [the most recent inspection] that they missed last fall because they weren’t looking closely enough.”

Sorcher said she was struck by the fact there were many issues that FDA found early this year that were completely absent from the inspection report last September, including revelations that the company itself had discovered Cronobacter in infant formula on two occasions, in 2019 and 2020, and destroyed the product.

Equipment in disrepair, water issues, and so on — all of it “should have been observable in September,” Sorcher said. “So the question is: Why didn’t they catch these things? And if they managed to miss all that, what else have they been missing?”

The FDA declined to respond to specific questions about the September inspection, and offered no explanation for the discrepancies between its September 2021 and early 2022 findings. The agency is planning to conduct a review of how it handled the incident “once the immediate public health risk is minimized,” an FDA spokesperson said in a statement to POLITICO.

Janet Woodcock, FDA’s principal deputy commissioner, told POLITICO in an interview last month that the review will be done out of her office and “it will be very intensive.” House Appropriations Chair Rosa DeLauro (D-Conn.), meanwhile, has asked the Health and Human Services Office of the Inspector General to conduct an independent investigation.

The FDA maintains its inspections are rigorous, and are only one piece of the food safety oversight system.

“The FDA remains committed to using all available tools to oversee the safety, effectiveness and quality of FDA-regulated products and help ensure that Americans have access to essential and safe products,” the FDA spokesperson said. The spokesperson emphasized that plant inspections aren’t the only way the agency monitors food production, noting, “they are one part of a robust and multi-pronged approach to overseeing the safety and quality of FDA-regulated products.”

It was an apparent coincidence that the very same week that FDA inspectors were in the Sturgis plant, Minnesota health officials notified the agency that an infant had been hospitalized with Cronobacter sakazakii after having consumed formula produced in the plant. Minnesota health officials reported the case to CDC Sept. 16 and to FDA Sept. 20, according to Doug Schultz, a spokesperson for the Minnesota Department of Health. FDA confirmed to POLITICO it received this report Sept. 20. The next day, the agency said it contacted Abbott Nutrition. The baby in Minnesota was hospitalized for 22 days but survived, state officials said.

The FDA declined to answer POLITICO’s questions about whether the inspectors who reviewed the Sturgis plant knew about the reported case, or whether they conducted any microbiological tests of equipment or product that might have detected Cronobacter in September.

If they weren’t told about the case that had been reported to federal officials, it’s unlikely they would have looked for it — plants are required to have their own systems in place for testing both equipment and product, but FDA inspectors don’t routinely do their own environmental swabs during inspections.

The September inspection report cited the Sturgis plant for not being in “clean and sanitary condition.” There was standing water in a few places in the facility. One employee was observed not washing hands or changing gloves after touching non-food contact surfaces. But there were no major red flags and the inspection got classified as what’s known as a VAI, or “voluntary action indicated,” which means Abbott Nutrition could voluntarily address the issues, according to inspection logs.

“Abbott is committed to upholding the highest standards for manufacturing of all nutrition products,” a spokesperson for the company said in a statement. “We have already begun implementing corrective actions and enhancements at the facility, leveraging new technology and strengthening our processes, to give parents and customers renewed confidence in the quality of manufacturing at our Sturgis plant when we restart operations there.”

Phyllis Entis, a microbiologist who runs the site eFoodAlert, which tracks food recalls, said that while Abbott apparently failed to properly maintain its plant, it’s clear that FDA missed problems in the runup to the massive formula recall, hospitalizations and deaths. The recall has also led to widespread shortages of certain types of formula, since the Sturgis plant produced a significant share of the total supply — a major stressor for parents and health care providers.

“Ultimately, it’s the company’s responsibility to maintain its equipment, and its food safety program, and all of the other ancillary stuff in proper working order. It’s the company’s responsibility,” Entis said. But she added, “It’s FDAs responsibility to oversee and make sure that that happens. So balls have been dropped all over the place.”

One of the biggest things FDA inspectors overlooked, according to Entis, who has closely reviewed the inspection documents, is that the plant had a history of disrepair for one or more milk dryers — machines that turn liquid milk into powder, one of the key ingredients in formula. Damaged milk dryers are a known problem in infant formula manufacturing. Back in 1977, a Salmonella outbreak in Australia was ultimately traced back to a cracked milk dryer where the bacteria had taken hold, Entis noted.

The September inspection report did not say anything about dryer deterioration. When FDA inspectors went back in late January, however, officials observed that the plant had a “history of internal deterioration” for dryers dating back to 2018, citing the plant’s own records. The agency noted that the company’s records showed that in August 2021, dryer inspections found “six instances of cracks and pits in the main chamber” for one dryer and several other cracks and damages were observed (further specifics were redacted). The inspection documents didn’t comment on the current condition of the dryers in question.

“It sounds like a situation that’s been deteriorating – has been allowed to deteriorate – for at least the last three, three and a half years,” Entis said.

The FDA’s most recent inspection — which spanned from late January to mid-March — observed many other problems that were absent from the agency’s routine inspection four months earlier. There were many more examples of water problems — officials noted there had been more than 300 “water events,” such as leaks, condensation and standing water in the production area in the past year, per the company’s own records. They also observed that plant workers had improper protective apparel, among other issues.

Perhaps most crucially, the agency found records suggesting that the plant had destroyed some formula product after it had tested positive for Cronobacter on two separate occasions — in September 2019 and June 2020. The report also noted the company had found the bacteria inside the plant a number of other times. FDA inspectors themselves found five different strains of Cronobacter in several locations at the plant when they returned in early 2022.

FDA has said that the bacterial strains found in the plant do not match the strains in the two illness cases that officials have tested for their genetic “fingerprint.” The agency has also said that formula samples inspectors collected at the facility tested negative for Cronobacter.

Abbott Nutrition has also repeatedly stated publicly that none of the infant formula it has sold to consumers has tested positive for Cronobacter. However, the Minnesota Department of Health told POLITICO that FDA and CDC did find Cronobacter sakazakii in an opened can of formula that was made in the Sturgis plant from the home of the Minnesota infant who became infected in September. Officials also found it in an opened bottle of water it took from the home.

“CDC and FDA tested formula from the case’s home: CDC tested an opened can of formula and an opened bottle of water, FDA tested unopened formula,” a state spokesperson said.

Federal health officials found that the unopened can of formula was negative. But the opened can of formula and the water that the CDC tested were positive for Cronobacter, which the spokesperson said indicated “some cross-contamination at the home between the water and the formula.”

It’s not clear why FDA has not disclosed this detail. The agency did not respond to a question about when it learned this information.

“We can’t discuss specifics of our ongoing investigation, but generally can share that when investigating these types of illnesses, multiple sources are frequently considered; including, but not limited to, open and closed formula containers, breast pump equipment, and water used for formula rehydration,” an agency spokesperson said.

The strain of Cronobacter found in the formula and water at the infant’s home did not match any of the strains FDA inspectors found in the Sturgis plant this winter, however, which has almost certainly complicated the federal investigation into the bacteria’s origin.

A spokesperson for the Centers for Disease Control and Prevention, which works with FDA to investigate foodborne illness outbreaks, confirmed that the bacterial strains the agency has tested don’t genetically match what FDA found in the plant.

“A sample from one patient was genetically related to Cronobacter found in opened powdered infant formula from the patient’s home,” the spokesperson noted. The agency doesn’t have any more cases to test “so it is unlikely that a definitive link between Cronobacter cases will be found,” the spokesperson said.

“It is possible that the cases included in this investigation occurred due to contamination of the formula after it was opened, which is how Cronobacter often gets into powdered formula,” they added.

Some outside the investigation, however, contend it’s more likely contaminated infant formula was to blame.

“To me, there are smoking guns,” said Bill Marler, a top plaintiffs attorney representing foodborne illness victims (though none affected by this particular incident). Marler noted that it’s common for individual food samples from a plant to test negative for certain dangerous bacteria or for the pathogen strains to not match, even when that product or plant is ultimately determined to be the source of the outbreak.

Microbiological testing is an important tool, he said, but a negative test doesn’t prove much because it represents just a small sample of the product produced at a given manufacturing location. “It happens all the time,” Marler said of the lack of genetic match.

Marler said that when he read the inspection reports, it was clear “there were problems that could have led to Cronobacter or other bacterial contamination.”

“It does raise questions about how rigorous FDA’s inspections are, but also about how rigorous Abbott’s food safety program was,” Marler said.