New information has come to light that implicates Bosch as having a much more direct role in VW's diesel cheating scandal.

A consortium of investigative journalists from Germany uncovered passages in evidence submitted to a US court that appeared to prove Bosch was aware that engine control software it had provided the auto maker was being used to manipulate emissions data.

Bosch warned VW in a letter dated June 2008 that "further development" of the software could cause VW vehicles sold in the US to lose their certification, according to the consortium, which included the daily "Süddeutsche Zeitung" (SZ) as well as the broadcasters NDR and WDR.

In a letter dated March 9, 2007, a Bosch employee reportedly advised two people at VW to remove any description of the software's malicious capabilities from official documentation. VW agreed to strike the passage from a version of the documentation provided to US regulators.

Until now, regulators had not yet fully established whether Bosch was aware of Volkswagen's intentions to modify the engine control software that Bosch had provided. In interviews, the car parts supplier had insisted it provided its clients with engine management systems according to their specifications.

"How these components are calibrated and integrated into complete vehicle systems is the responsibility of each auto maker," the company told the Reuters news agency last year.

The newly uncovered information, however, suggests Bosch knew exactly what VW was doing with the software and made an effort to keep the deception under wraps.

In February 2006, the two companies agreed that only 35 specially chosen VW employees and contractors would have access to the "advanced software features" of the defeat device - the area of code that regulated engines' output of harmful emissions. Any changes to the code would have to be first cleared by Bosch, according to SZ, NDR and WDR.