BUFFALO, N.Y. — Tonawanda Coke was found guilty of violating the probation issued as part of the company's criminal sentencing in 2014.

The company was convicted of 14 environmental violations, including 11 violations of the Clean Air Act in 2013.

U.S. District Court Judge William Skretny ruled Monday that Tonawanda Coke violated its probation through emissions from its waste heat stack, a decision that encouraged community activists.

"We look forward to having a clean, healthy environment in Tonawanda, and we look forward to a positive resolution in the sentencing phase of this procedure," said Maria Tisby of the Clean Air Coalition.

Federal prosecutors presented data showing that opacity from the stack has exceeded 20 percent continuously since May, a violation of the Clean Air Act.

Attorneys for Tonawanda Coke never disputed that data and centered their case on whether increased opacity could correlate to health issues for area residents.

"We still don't have any proof in the record that that increased opacity, at least on behalf of the government, is creating any type of imminent and substantial harm, or any type of significant effect on any health or the community," said Jeff Stravino of Hodgson Russ LLP.

Tonawanda Coke hired Westbrook Thermal Technology, LLC as a consultant in June to draft a remedial action plan.

Company president Richard Westbrook says he believes coke oven repairs that would bring the company into compliance can be done by October 13.

Prosecutors argued that the company continues to be reactive instead of proactive, and that these actions should have been taken a long time ago.

Sentencing will take place Friday morning.

The state Department of Environment Conservation also ordered the plant to shut down in July because of emission violations, but it’s still up and running.

Tonawanda Coke has an appeal hearing scheduled with the DEC in October.