Following accusations by the US environment protection agency (EPA) the German carmaker admitted on 22 September 2015 that 11m of its diesel cars were equipped with software that detected if the vehicle was being driven under lab test conditions and adjusted itself to reduce emissions of harmful nitrogen oxide (NOx) pollution.
Under real-world conditions the NOx emissions were considerably higher.
The company has since admitted that Winterkorn was informed of the illegal emissions at least a year before having been sent a memo detailing the cars’ higher nitrogen oxide emissions in May 2014.
In addition it was revealed on Monday that European commission experts issued warnings about potential emissions test cheating as far back as 2010.
Companies registered on the stock exchange are obliged by law to inform investors of previously unknown events or circumstances that could considerably influence the price of shares.