Minnesota regulators started the process Wednesday of revoking a key air permit for the Northern Iron foundry in St. Paul, a rare rebuke of an operating business that could ultimately force it to close.

The Minnesota Pollution Control Agency said in a statement that the foundry has repeatedly failed to supply needed information for a new air pollution permit. The foundry and regulators have been battling for months over environmental data, operating hours and soot found on neighbors' homes.

"We do not have reasonable assurance that the company can comply with a permit," spokeswoman Becky Lentz said in a statement.

The foundry, located in the Payne-Phalen neighborhood and owned by Lawton Standard Co., said it would fight the state's action. It has 30 days to request an administrative hearing, and is allowed to keep running during that time.

"Lawton Standard successfully operates in six other states, and we have productive regulatory relationships in every one except Minnesota," Alex Lawton, the CEO of Lawton Standard, said in a statement. "Unfortunately, Minnesota has earned a reputation for being a state where businesses consistently struggle to operate and successfully secure permits and approvals."

While Northern Iron won't immediately stop melting and molding metal, Brittany Bruce said she felt "like the community is being heard." She lives directly behind the foundry on Wells Street.

The MPCA said at the beginning of the year that nearby homes such as Bruce's were being coated with soot by the metal shop. Bruce has since signed on as a plaintiff in a class action lawsuit against Northern Iron.

"We know historically they fight tooth and nail, so we know that this is not the last step," Bruce said. "But this is our first victory out of many."

Northern Iron, which opened in 1906 at 867 Forest St., molds custom metal components. Lawton Standard bought the site in 2022 and today it employs about 80 people.

The state and the business started clashing in 2023, when Northern Iron was fined $41,500 for illegally expanding its operations. The foundry and MPCA also struck a deal for the company to fix pollution equipment.

But Northern Iron's own modeling later showed it was exceeding the limits for lung-damaging fine particles and airborne lead by thousands of times the legal levels. The company insists it isn't illegally polluting, however, and its statement Wednesday stressed that air monitors had not found improper pollution.

In April, the MPCA ordered the company to take several actions to limit pollution, including curbing its hours. Northern Iron sued and got a Ramsey County judge to bar that provision, but other parts of the order remained in place.

Court hearings in the case since then have been tense, with the MPCA saying that the foundry isn't providing key data like a study on whether air is contained in the building, and the foundry contending the state is bullying it in its quest for information.

"I would like a reduction in the mudslinging, that would be helpful," Ramsey County District Judge Leonardo Castro said during a hearing in February.

Mel Lorentz, an environmental attorney who lives on St. Paul's East Side, has closely watched the case.

"It really is a rare thing for an agency to revoke a permit," she said. "It really speaks to what a poor neighbor Northern Iron has been, and how difficult they have been for the [MPCA] to deal with."