Reports say a high-ranking employee notified VW managers as early as May 2014 that U.S. regulators could examine car engine software.
DETROIT, MI - German automaker Volkswagen AG is at the center of a Justice Department probe after the company admitted in September that it equipped some of its diesel engines with software that cheats U.S. emissions tests.
Company leaders have been on Capitol Hill to testify, and have said the scandal was limited to a small group of engineers.
A report in Reuters Sunday said that a high-ranking employee notified VW managers as early as May 2014 that U.S. regulators could examine car engine software.
German newspaper Bild am Sonntag reported the warning was sent as an internal letter to then-CEO Martin Winterkorn.
Anonymous sources confirmed to Reuters the letter exists, but they could not say whether Winterkorn, who resigned as company CEO in wake of the scandal, had himself seen it.
As he stepped down, Winterkorn said in September that vacating his spot was in the best interests of the company, though said he is not aware of any wrongdoing on his part.
The company has declined to comment on the ongoing investigation.
The letter, which was reportedly sent by an employee known as "Winterkorn's fireman," was found through an internal investigation being conducted by law firm Jones Day. VW told Reuters the investigation will be complete by the end of April.
Meanwhile, the automaker faces up to $46 billion in penalties from U.S. regulators. The company also faces hundreds of civil suits, and has hired well-known Washington, D.C. attorney Kenneth Feinberg to oversee a claims resolution facility for customers affected by its diesel emissions scandal.
VW has admitted to using software, known as a defeat device, in the 2009-2015 Audi A3 and the Volkswagen Beetle, Golf, Jetta and Passat TDI cars with 2.0-liter diesel engines to trick emissions tests. There are about 11 million of the cars globally and 482,000 in the U.S.
Related: VW apologizes for diesel scandal, unveils Tiguan SUV concept in Detroit
The VW cars with 2-liter diesels would meet emissions standards tests in a laboratory or testing station, but in normal operation, they emit nitrogen oxides at up to 40 times the standard, according to the EPA.
The company has also admitted to using the software in some of its vehicles with 3.0-liter diesel engines.
David Muller is the automotive and business reporter for MLive Media Group in Detroit. Email him at dmuller@mlive.com, follow him on Twitter or find him on Facebook.