VW Developed 4 Separate Defeat Devices Over 7 Years

If true, the incremental updates to the software cheat could be evidence of a larger group of employees making an ongoing effort to continue their deception without regulators' knowledge.

So far, VW's emissions scandal has embroiled some 11 million vehicles using the EA189 and EA288 diesel engines. "VW would have had to reconfigure the software for each generation of engines," an unnamed official close to the US investigation said to Reuters.

Recently, Volkswagen asserted that only a few individuals were involved in the cheat, and challenged a report that at least 30 managers knew about the situation. The report in Reuters, if true, would make VW's claims hard to believe. It might also mean even more legal trouble for VW. According to the report, the Justice Department could seek even harsher punishments if it finds out that more top execs knew more about the issue than VW is letting on.

Investigators in Europe have also been working out who was involved in the deception. Italian authorities recently searched the Lamborghini headquarters and VW's main office in the country looking for evidence. Meanwhile, German prosecutors collected documents directly from the automaker's headquarters in Wolfsburg, and regulators there mandated a recall in early 2016.