Following federal allegations announced Friday that Volkswagen cheated on emissions testing, it has stopped sales of four-cylinder diesel Jetta, Passat and Beetles.

The allegations covered Volkswagen Jetta, Beetle and Golf models from 2009 forward, 2014-15 Passats, and Audi A3s diesels from 2009-2015.

According to the The Detroit News, a company spokesperson did not say how many of the new vehicles were subject to the sale halt.

In an unusual move, the U.S. Environmental Protection Agency denied VW a “certificate of conformity” to sell 2016 models with the 2.0-liter diesel engines. Dealers had been anticipating these to replenish inventories.

At issue is a “defeat device” Volkswagen was charged with installing that made emissions controls only operate when under testing procedures. Otherwise the cars could emit 10-40 times the allowable pollution.

In a statement, CEO of Volkswgen AG Dr. Martin Winterkorn said he has ordered an external investigation and that the company does not tolerate law violations.

He said it was a matter of personal priority, and apologized while saying he would act with transparency toward investigators.

“I personally am deeply sorry that we have broken the trust of our customers and the public,” said Winterkorn. “We will cooperate fully with the responsible agencies, with transparency and urgency, to clearly, openly, and completely establish all of the facts of this case.”

The case however is just beginning, and the Justice Department could reportedly open a criminal investigation, if it has not already.

The EPA says a recall of nearly 500,000 affected cars is also expected. The process could take up to a year between the recall and making suitable repairs, depending on the fix deemed necessary.

California meanwhile is procuring other branded vehicles as well to check for potential defeat devices such as were discovered on the Volkswagen and Audi cars.

The incident was first uncovered by West Virginia University. Volkswagen admitted the issue when questioned by EPA and California Air Resources Board representatives.

The Detroit News