The former CEO of Volkswagen’s  Martin Winterkorn is being  officially investigated for fraud by German prosecutors who have increased their enquiries into the company’s emissions cheating debacle and have included him and another 36 additional people.

 Interestingly this is the first time prosecutors have named Mr Winterkorn, who resigned days after the scandal when it became public in September 2015, in the case relating to the the cheat software in eleven million vehicles.

Prosecutors revealed on Friday that there were “sufficient” indications that the suspects in the case were aware that VW diesel vehicles had been fitted with “defeat device” software earlier than has been indicated.

VW has admitted that 11m cars were fitted with software that reduced nitrogen oxide emissions in laboratory tests.

Earlier this month Mr Winterkorn told German politicians that he did not know what a “defeat device” was until September 2015. But he declined to say when he first heard of emissions irregularities, which were discovered by US regulators in the spring of 2014.

Prosecutors also added that fresh evidence was gathered in raids on public and private offices which led them to broaden their investigation from 21 individuals to 37. The prosecutors said the material would take several more weeks to examine.

According to a US criminal complaint against a lower-level VW employee  this month, the executive management in Wolfsburg authorised the continued concealment of the illegal software in late July 2015.

But the US complaint did not make clear if that group included Mr Winterkorn or anyone on the management or supervisory boards.

VW has said its executive board did not learn of the software violations until late August 2015 and formally reported the cheating to U.S. authorities in early September that year.

Shareholders have sued VW to recoup billions of euros in losses, with the stock plunging more than 40 per cent after the scandal was revealed by US regulators, although it has recovered somewhat. Their lawyers have said they believe investors would have a stronger case if VW’s top management was involved.

raunschweig prosecutors said on Friday they had searched 28 homes and offices in connection with their investigation this week. The number of people accused in connection with the emissions scandal had risen to 37 from 21, including Winterkorn.

“Sufficient indications have resulted from the investigation, particularly the questioning of witnesses and suspects as well as the analysis of seized data, that the accused (Winterkorn) may have known about the manipulating software and its effects sooner than he has said publicly,” they said in a statement.

It will take weeks to sift through everything found in this week’s raids,prosecutors said. Winterkorn, 69, and the 36 other people are under investigation on suspicion of fraud and violating competition law, prosecutors said.

Europe’s largest automaker took a huge step this month toward ending its biggest-ever corporate crisis when it agreed to plead guilty in a $4.3 billion deal with the U.S. Justice Department.

In total, VW has now agreed to spend up to $22 billion in the United States to address claims from owners, environmental regulators, U.S. states and dealers.