3M has been subpoenaed by a federal grand jury in connection to discharges from a chemical plant in northern Alabama that may not have complied with permit requirements.

Michael Roman, the Minnesota-based company’s CEO, announced the subpoena during an investor conference call Tuesday, WHNT-TV reported.

The company faced lawsuits and public scrutiny last year after it was accused of releasing chemicals from its factory in Decatur into the Tennessee River without disclosing its actions.

“As previously disclosed in 2019, 3M discovered and voluntarily informed the EPA (Environmental Protection Agency) and appropriate state authorities that discharges from our Decatur, Alabama, facility may not have complied with permit requirements,” Roman said during Tuesday’s call. “We immediately idled the relevant processes and took steps to address these issues.”

In September 2019, 3M halted some work related to fluoropolymer manufacturing at its Decatur plant to work with environmental regulators on compliance issues.

Substances known as PFAS are used to make fluoropolymer coatings and products that resist heat, oil, stains, grease and water.

The subpoena was filed in late December by the U.S. Attorney’s Office for the Northern District of Alabama, Roman said. U.S. Attorney Jay Town declined WHNT-TV’s request for comment.

“We are cooperating with this inquiry,” Roman said.

It’s unclear whether the grand jury has completed its work or whether the investigation is still ongoing.