The fight over cleaning up the nation’s fuel economy standards just got a whole lot dirtier.

, the Justice Department has launched a preliminary antitrust probe into whether the four automakers that reached an independent agreement with the California Air Resources Board, an agreement which defied the Trump administration’s attempts to freeze fuel economy standards until 2026, violated antitrust law with cartel-like behavior.

From the Wall Street Journal:

Justice Department lawyers are seeking to determine if Ford Motor Co., Honda Motor Co., BMW AG, and Volkswagen AG violated federal competition law by agreeing with each other to follow tailpipe-emissions standards beyond those proposed by the Trump administration, the people said.

This report comes on the heels of a that the EPA and Department of Transportation are working on ways to revoke CARB’s ability to set their own fuel economy regulations independent of the federal government’s.

A source involved with the investigation speaking to the Journal claim the Justice Department undertook this effort independently of the Trump administration. But this assertion that strains credulity considering the report from yesterday about the Trump administration’s direct efforts to undermine CARB and their agreement with the automakers. In either event, it sure is awfully convenient for the Trump administration that the Justice Department is trying to poke holes in the agreement as well.