For Volkswagen, Dieselgate just won't end.

On Thursday, four employees of the VW-owned Audi brand were indicted by a federal grand jury on charges connected to diesel emissions cheating.

The case echoes the massive scandal that has led to prison terms for two ex-VW employees, charges against others, including a former CEO, and billions of dollars in fines. But in highlighting the breadth of the issue across the industry, the indictments come only a week after a civil settlement was reached in a similar case against Fiat Chrysler Automobiles -- the criminal case is ongoing -- that is expected to cost the automaker almost $800 million.

It also comes as thousands of people connected to the automotive industry are in Detroit for the 2019 North American International Auto Show.

The four Audi employees -- Richard Bauder, Axel Eiser, Stefan Knirsch and Carsten Nagel -- were named in a 12-count indictment, accusing them of conspiracy to defraud the United States, to commit wire fraud and to violate the Clean Air Act. A fifth individual, Zaccheo Giovanni Pamio, was named in the indictment but not charged.

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The allegations, which focus on the period from 2006 to 2015, highlight the use of so-called defeat devices designed to change the performance of diesel engines so they could meet U.S. emissions requirements and be sold here. The result would be vehicles marketed as "clean diesel" which polluted at levels higher than allowed.

"... They knew that these representations made to U.S. customers were false, that the subject vehicles were not 'clean,' that Audi's diesel vehicles were intentionally designed to detect, evade, and defeat U.S. emissions standards, and that the subject vehicles were polluting the environment with (nitrogen oxide) emissions well above U.S. limits," according to the filing Thursday in U.S. District Court in Detroit.

The paperwork also references an email from Oliver Schmidt, one of the former VW employees previously sentenced to prison. The email, sent to Knirsch, who had been head of Audi's Engine Development Division in Ingolstadt, Germany, followed warnings from regulators that they might not certify certain 2016 model year 3.0-liter vehicles.

Schmidt wrote, in a translation from German, that "our worst fears have come true" and "we urgently need help with arguments."

The paperwork says members of the group later provided false information in order to obtain certification for model year 2016 Audi 3.0-liter diesel vehicles.

Spokespeople for Audi did not immediately return messages seeking comment.

No court dates have been set in the case. The employees are based in Germany, according to a court official.

Contact Eric D. Lawrence: elawrence@freepress.com. Follow him on Twitter: elawrence@freepress.com.