The Clean Air Council sued United States Steel Corporation Monday for violations of pollution reporting requirements stemming from a fire at the company’s Clairton Coke Works last December.

In their complaint, filed in the US District Court for the Western District of Pennsylvania in Pittsburgh, the Clean Air Council alleges that US Steel failed to comply with pollution discharge reporting requirements in the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, commonly referred to as the Superfund law). Clean Air Council alleges that US Steel failed to report that the facility had released dangerous amounts of hydrogen sulfide, benzine and other coke production byproducts into the air in the months following a fire that destroyed pollution control systems at the factory. CERCLA requires that companies notify the National Response Center of any releases of toxic pollutants promptly after their discharge. The lawsuit claims that US Steel failed to notify the National Response Center of any of these discharges and is therefore in violation of CERCLA and potentially subject to more than $50 million in fines.

In a statement issued with the complaint, Clean Air Council said that US Steel’s continued discharge of pollutants has led to the Clairton region having the “air quality ranked worst in the US” and caused major health issues. “It’s critically important that industries promptly report releases of air pollution,” said Lisa Widawsky Hallowell, the lead attorney on the case, “so that people living downwind can protect their families, and so that local health authorities can take appropriate actions to protect public health.”

In a statement to the Pittsburgh Post-Gazette, US Steel said that they do not comment on pending litigation but that they are committed to investing $1 billion in upgrades and improvements to the Clairton Coke Works to improve production and reduce environmental impacts of their operations over the next three years.

US Steel and the Allegheny County Heath Department recently settled a separate lawsuit over the December fire and the health impacts caused by the pollution from the plant.