A German newspaper claims to have uncovered a PowerPoint presentation from 2007 detailing the emissions cheat strategy.

Audi has reportedly fired four top diesel engineers after one accused current CEO Rupert Stadler of playing a role in the diesel emissions scandal.

The allegations have surfaced in a labor court dispute, where lawyers representing Ulrich Weiss showed evidence that he was simply a 'pawn' in the scheme and Stadler knew of the illegal defeat device in 2012, according to a Handelsblatt report.

Weiss, formerly Audi's head of powertrain development, had been suspended in 2015 after the scandal came to light. He had remained on company payroll for more than a year, however, and was formally fired after the labor court allegations surfaced in German media reports.

A Spiegel report, meanwhile, claims to have uncovered an internal PowerPoint presentation detailing the diesel cheating strategy as far back as 2007. The slides allegedly argue in favor of a two-mode system to manage urea injection, allowing the emissions hardware to eliminate 90 percent of nitrogen oxides on a lab dyno but only remove "30-70 percent" during normal driving conditions.

Without the cheat, internal tests allegedly showed that the Volkswagen Touareg would have required an AdBlue (urea) refill every 1,243 miles -- far below the target duration of a top up during every scheduled service visit.

Weiss was one of four engineers reportedly fired as the scandal continues to evolve, but Audi has not yet signaled any intention to dismiss Stadler.