3M Co. is idling some manufacturing at an Alabama plant while it works with regulators on compliance issues related to chemical byproducts discharged into the Tennessee River, company officials confirmed Friday.

3M officials said the partial shutdown of the plant in Decatur, Ala., is voluntary and that the chemicals discharged into the river did not exceed accepted levels. The plant makes water- and stain-resistant "fluoropolymer" chemicals that fall under a closely watched classification called PFAS.

The Maplewood-based company would not say if the plant idling was expected to last days or months.

"While we continue to work with the EPA and the Alabama Department of Environmental Management (ADEM) on previously disclosed issues, we have elected to temporarily idle certain manufacturing processes," the company said in a statement on Friday. "We will resume these processes as soon as practicable."

It was not immediately clear whether 3M's decision to idle manufacturing operations was related to any enforcement action by pollution regulators.

Lynn Battle, a spokeswoman for the Alabama Department of Environmental Management, declined to discuss the matter. Battle said the agency was informed of 3M's action, and that "no further information is available from ADEM at this time."

James Pinkney, a spokesman for EPA Region 4, which oversees Alabama, called 3M's action "a business decision."

In April, 3M agreed to pay $35 million to settle a water contamination lawsuit in northern Alabama, where the West Morgan-East Lawrence Water and Sewer Authority supplies drinking water to rural areas outside Decatur.

The lawsuit had accused 3M of discharging chemicals into the Tennessee River, which then contaminated the regional water supples in several towns.

In July, 3M announced it would begin testing three former landfills near the Decatur plant. The tests were expected to reveal whether any disposed 3M chemicals leaked from the closed landfills into the river or local groundwater.

David Whiteside, founder of the Decatur-based Tennessee Riverkeeper, said he was frustrated by the lack of information about 3M's partial factory shutdown. Whiteside's nonprofit sued 3M and other defendants in 2016 to force a cleanup of parts of the Tennessee River and Wheeler Reservoir.

The parties are in mediation.

"I think 3M is being purposely vague and that seems to be a big part of their playbook in trying to run away from their PFAS problems in Alabama and nationwide," Whiteside said.

3M officials countered that "3M takes seriously its environmental compliance obligations and continuously assesses its performance."

In April, 3M voluntarily disclosed to the U.S. Environmental Protection Agency (EPA) that its Decatur plant released one type of PFAS chemical, and possibly a second, into the Tennessee River. That violated a 2009 consent order, according to a copy of the letter filed with the Alabama pollution regulator.

In the letter, 3M said it stopped making those two chemicals in Decatur after it discovered the releases. The company also said it was investigating the matter and asked to meet with regulators about it.

3M spokeswoman Fanna Haile-Selassie said 100 of the company's 950 employees will be affected by the partial shutdown at the Decatur plant.

"At this time, we intend on shifting roles and responsibilities to maintain employment of all affected 3M Decatur workers. It only affects our 3M Decatur facility," Haile-Selassie said.

In addition to making fluoropolymer chemicals, 3M's Decatur plant also makes optical films or film components. None of the film workers at the plant will be affected by the temporary idling, Haile-Selassie said.

3M said Friday it is continuing to work with the EPA and Alabama's environmental management on various issues at the Decatur plant.

Haile-Selassie confirmed the issues were related to byproducts from 3M fluoropolymer chemicals that were discharged into the Tennessee River. She also said 3M is reviewing all of its operations at the plant, including those dealing with non-PFAS chemicals. The goal is to ensure operations are handled in compliance with regulatory and best practices.

3M, Dupont, Tyco Fire and other PFAS chemical makers have been sued repeatedly in recent years because PFAS chemicals have been found to have leached or discharged from facilities, customer plants or approved dump sites and into ground and municipal drinking water sources around the United States.

Last year, 3M agreed to pay the state of Minnesota a historic $850 million to settle water-contamination claims and assist with cleanup costs. Earlier this year, 3M settled with the city of Lake Elmo over its PFAS contamination lawsuit.

Water-contamination lawsuits have since popped up across the country including in Alabama, New Jersey, Michigan, New Hampshire and Vermont.

This year, 3M reserved hundreds of millions of additional dollars in potential legal funds as the company defends itself in various courts or agrees to help with PFAS cleanup efforts at some of its facilities.

The U.S. House and Senate are working on several bills that call for all PFAS chemicals to be deemed hazardous. The bills also would require all PFAS chemical manufacturers to pay for cleanup costs at military bases contaminated with PFAS chemical foams that are used to put out fires.

The PFAS chemicals made by 3M and others are used to make Scotchgard products, firefighting foams and/or a host of heat-, stick- and stain-resistant cookware, carpets, clothing and household products.