The agency's Office of Inspector General has outlined a broad audit of existing test and certification procedures.

The Environmental Protection Agency is preparing to audit its own emissions testing programs to uncover potential vulnerabilities that could be exploited by automakers.

The agency's Office of Inspector General has published a memo outlining the internal inquiry, which aims to "determine whether the EPA's existing internal controls are effective at detecting and preventing light-, medium-, and heavy-duty on-road vehicle emissions fraud."

The OIG expects to focus on the National Vehicle and Fuel Emissions Laboratory and other divisions directly involved in testing and certifying new cars for emissions compliance.

"The anticipated benefit of this project is to provide information to the public regarding the effectiveness of the EPA's existing internal controls for its on-road vehicle emissions testing program," the memo adds.

The notice did not name Volkswagen, but the inquiry undoubtedly intends to explain how Volkswagen allegedly implemented several generations of 'defeat' devices for seven years before regulators caught on. Notably, the cheat was discovered not by the EPA but rather a group of West Virginia University researchers funded by an International Council on Clean Transportation grant.

The agency appeared to take a more proactive approach in its ongoing dispute with Fiat Chrysler Automobiles. Again, however, the notice of violation was filed after signs of trouble had been reported elsewhere.

The EPA's Inspector General has not disclosed an expected time frame for completing the audit.