A formal investigation into possible market manipulation in Volkswagen’s shares was launched on Wenesday by Germany’s financial regulator after a huge swing in the carmaker’s market value of some €370bn ($478.8bn) this week alone.

The probe by Bafin follows sharp criticism over the transparency of the country’s capital markets after a vertiginous surge in VW’s share price triggered by the weekend disclosure by Porsche that it had a much larger interest in its fellow carmaker than many traders had realised.