Prosecutors in the northern city of Turin announced the investigation Tuesday after customs officials independently confirmed the findings by the magazine "Il Test," which published a cover story last spring revealing that nine out of 20 bottles it tested were not extra-virgin as labeled.
The good news is that here in the USA, California olive oil producers generally believe in truth in advertising. Also, there is a good website that recommends virgin olive oils that it deems to be true olive oils. In fact, the guy who runs the blog, Tom Mueller, has written a book about it all.
Here's a link to his recos on supremarket olive oils.