Shares in German automaker Daimler skidded by more than five percent on the Frankfurt stock exchange on Friday after the group said it was launching an internal probe into its emissions certification process.

The shares were showing a loss of 5.5 percent at 52.98 euros shortly after trading opened, after Daimler said late Thursday that it was launching an internal investigation, "into its certification process related to exhaust emissions in the United States upon the request of the US Department of Justice (DOJ)."