Stadler was questioned earlier this week by U.S. law firm Jones Day, which was hired by VW to conduct the investigation, about when he found out about the use of emission test cheating devices in the scandal.
The report by Jones Day into Stadler was discussed during the VW board meeting yesterday and a source told Reuters that "Nothing burdensome against Stadler was found" in the report.
Stadler has been the chairman of the board and chief executive officer (CEO) of Audi AG since 1 January 2010, and as its chief financial officer (CFO) since 12 January 2007. Stadler, joined the VW group's nine-member executive board in 2010.
Audi admitted that its 3.0-litre V6 diesel engine used the illegal emissions cheating software after denying the allegation for a few weeks, when it first surfaced in November 2015.
Unlike parent company Volkswagen, Audi is still trying to find a technical solution to fix about 85,000 V6 diesel engines, which were also used by Porsche and VW brands.
The Volkswagen group is still facing other investigations and lawsuits regarding the emissions scandal and has already agreed to $15 million settlement with the U.S. government to fix its polluting 2.0-litre EA189 diesel engine.