Navistar International Corp. confirmed this afternoon that it is under investigation by the U.S. Environmental Protection Agency (EPA) over whether 7,600 engines manufactured in 2009 were properly certified under the Clean Air Act. Each violation carries a fine of up to $37,500— putting Navistar on the hook for as much as $285 million in fines.

Navistar acknowledges that it has received notice from U.S. EPA related to the use of 2009 transition engines,” Navistar spokesperson Jim Spangler told FleetOwner.

“We firmly believe our 2010 transition was appropriate, and we will continue our discussions and cooperation with the agency on this matter,” he added.

According to a news report posted by Reuters this afternoon, EPA informed Navistar of the investigation in a letter dated Jan. 30th. Per Reuters, the engines now under review were “so-called transition engines, or engines built at a time when the company was preparing to launch a new engine line. Navistar has said in the past the company was in constant communication with the EPA during the period in which these transition engines were built.”

Reuters added that in its letter, “EPA said that Navistar partially built the 7,600 engines in 2009, but did not fully complete the production of the engines until 2010.” The agency noted this could be a violation of the Clean Air Act