Abbott Laboratories is under investigation by the US Department of Justice, the company confirmed Friday, nearly a year after shutting down a Michigan baby formula plant after illnesses were reported.

Abbott did not specify what aspect of the company is under Justice Department scrutiny.

«The Department of Justice has informed us of their investigation and we are cooperating fully,» an Abbott spokesperson said in a statement to NBC News.

The Wall Street Journal reported the Friday before the Justice Department was investigating conduct at the Abbott plant in Sturgis, Michigan, citing unnamed people familiar with the matter. NBC News has not independently confirmed the nature of the investigation. The Justice Department did not immediately respond to a request for comment from NBC News.

Abbott voluntarily shut down production at its Sturgis infant formula manufacturing plant on February 17, 2022, after infants consuming formula prepared at the plant became ill.

The shutdown contributed to a nationwide shortage of infant formula.

Four babies, two of whom died, became ill with a rare bacterium after consuming powdered formula made at Abbott’s Michigan factory.

Federal investigators could not definitively determine the source or sources of the bacterium, Cronobacter sakazakii, which can cause serious illness.

The company signed a consent decree with the federal government in May outlining what it would do before reopening its plant.

The Food and Drug Administration said that when the proposed consent decree It was announced that «the government alleges that powdered infant formula products manufactured at Abbott Nutrition’s Sturgis facility were adulterated because they were manufactured under unsanitary conditions and in violation of current good manufacturing practice requirements.»

Production at the Michigan factory, which makes three of the country’s most popular brands, Similac, Alimentum and EleCare, resumed in June.

Abbott Labs previously said that it «continues to[s] to improve our manufacturing and quality processes to ensure that our products remain free of Cronobacter Sakazakii» and «had already begun implementing corrective actions and facility improvements.»

The company also said the genetic mismatch between the sick babies and the formula confirmed its own internal tests that showed there was no link, and said it did not find the bacteria in any of its distributed products.