At the end of the NY Times piece:

Richard Corey, an executive officer on the California Air Resources Board, credited “dogged detective work in the lab” for the discovery of the software, which he said resulted in the admission from Volkswagen that the company was using the devices.

E.P.A. officials declined to reveal why they chose to initiate the investigation.

The Volkswagen case is not the first federal investigation into the use of defeat devices. In 2007, the federal government reached a landmark settlement requiring Casper’s Electronics, of Mundelein, Ill., to stop selling the devices, and to pay a $74,000 civil penalty. The company had sold approximately 44,000 defeat devices through its website and retailers since 2001.


Cheers,
Scott.