Ford Motor Co. disclosed today that the U.S. Department of Justice has opened a criminal investigation into its U.S. emissions certification process, the third such probe of an automaking giant in recent years.

The investigation focuses on issues relating to Ford’s analytical modeling and methods of testing a vehicle’s resistance, according to the company’s latest 10-Q report to the U.S. Securities and Exchange Commission. Ford emphasized in the filing that the DOJ’s probe does not involve so-called defeat devices such as the ones Volkswagen used to cheat on emissions tests in 11 million of its vehicles.