The U.S. Environmental Protection Agency (EPA) sued Navistar International Corp. Wednesday over the 2010 sale of heavy-duty trucks, which it says violated the Clean Air Act. The lawsuit reportedly seeks as much as $37,500 a day for each violation in civil penalties.

According to the lawsuit filed in District Court for Northern Illinois in Chicago, Navistar sold nearly 7,750 diesel engines -- built in 2009 -- violating the EPA emissions standards that took effect on Jan. 1, 2010, the Wall Street Journal reported. The suit will reportedly be an additional burden on Navistar, which is coping with three years of losses following declining sales.

The court filing stated that Navistar “sold, offered for sale, introduced or delivered engines that did not satisfy emissions standards applicable to model-year 2010 engines,” according to the Journal.

Navistar defended itself saying that the manufacture of the engines in question began in 2009 and was completed in 2010. “We believe our 2010 engine transition was appropriate,” a spokesman told the Journal.

The company reportedly maintained that these engines should be allowed as “transitory” units qualified for the 2010 trucks. However, the EPA stated that Navistar did not secure the proper exemptions to use the engines.