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.

A DOJ representative did not immediately respond to an emailed request for comment about the inquiry.

In January 2017, Volkswagen pleaded guilty to three criminal felony counts and agreed to pay $4.3 billion in criminal and civil penalties. The scandal also earned the German automaker's former top U.S. compliance officer a seven-year imprisonment term and $400,000 fine for his alleged role in the conspiracy.

And last January, Fiat Chrysler Automobiles paid $800 million to settle state and federal regulators' allegations that it violated clean air laws by installing and failing to disclose emissions software that allows excess pollution.

In Ford's case, it announced in February that, after employees raised concerns last September about fuel economy and emissions compliance, it brought in an outside firm to investigate the matter.

At the same time, the company also voluntarily disclosed the issue to the U.S. Environmental Protection Agency and California Air Resources Board, as well as “a number of other state and federal agencies,” according to Friday's SEC filing.

“We are fully cooperating with all government agencies,” it said. “Because this matter is still in the preliminary stages, we cannot predict the outcome, and we cannot provide assurance that it will not have a material adverse effect on us.”