(CNN) — A former employee at Abbott Nutrition filed a whistleblower complaint about the company’s Sturgis, Michigan, plant with the U.S. Department of Labor’s Occupational Safety and Health Administration in February 2021, months earlier than previously known, a source familiar with the matter told CNN on Wednesday.

The complaint was filed on Feb. 16, 2021, and was passed on to Abbott and the US Food and Drug Administration three days later, the source said.

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The news was first reported Wednesday by the Wall Street Journal, which also said the whistleblower was terminated in August 2020 and filed a discrimination complaint with Michigan OSHA shortly after.

Abbott submitted a formal response to the February complaint in April 2021, according to documents and an unnamed source, the Journal said. The whistleblower then filed a complaint with the FDA in October 2021 that expanded on the safety claims made in the February complaint, the Journal reported.

The October 2021 complaint was released in late April by US Rep. Rosa DeLauro, who called its allegations “extremely disturbing.”

Abbott said Wednesday that it wasn’t aware of that complaint until its release in April, “and there’s an open investigation into these allegations.”

The FDA interviewed the whistleblower in December 2021, and FDA inspectors conducted in-person “for cause” inspections of the Sturgis facility between January and March 2022. At the same time, the FDA was learning about four dangerous Cronobacter infections in infants who had consumed formula, and Abbott recalled three of its popular formula products.

While the inspection was ongoing, Abbott closed the facility to address problems identified by the FDA. The recalls and closure hindered an industry already hobbled by supply chain problems, contributing to a nationwide formula shortage.

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In April, Abbott submitted a corrective action plan to the FDA, and they entered into a consent decree regarding the plant’s reopening in May. The Sturgis facility resumed producing infant formula on Saturday.

The company said Wednesday, “Abbott takes employee concerns very seriously and we foster a culture of compliance to produce the best and highest-quality products. … We believe this to be a former employee who was dismissed due to serious violations of Abbott’s food safety policies.

“While at the company, the former employee did not bring forward product safety complaints to our Office of Ethics and Compliance. After dismissal in August 2020, the former employee brought forward a complaint to Michigan OSHA in October 2020 unrelated to product safety. That complaint was dismissed. The federal OSHA complaint from February 2021 was a new complaint that raised new and different topics. And it continued a pattern of ever-evolving, ever-escalating allegations. We investigated the federal OSHA complaint and have not been able to confirm the allegations.”

DeLauro said Wednesday’s news is “damning.”

“We must get to the bottom of who knew what and when, and we will not be able to do that if everyone involved wants to skirt accountability,” she said.

An FDA spokesperson acknowledged the questions surrounding the timeline Wednesday but said, “Our top priority right now is addressing the dire need for infant formula in the U.S. market, and our teams are working night and day to help make that happen — including ensuring Abbott takes the appropriate corrective action to address insanitary conditions observed by the FDA.”

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