U.S. federal prosecutors will investigate criminal allegations against Yves Bouvier, Luxembourg's former "Freeport King," who sold billions of dollars worth of art to Russian billionaire Dmitry Rybolovlev, and other clients, according to Keri Geiger for BloombergBusiness.

Accused of fraud, money laundering and inflating prices on art --- including works by Matisse, Gauguin, Modigliani, van Gogh, Klimt and Rothko --- the ongoing criminal investigations against Bouvier in Europe have rattled the art world for many months. In Sept., a judge in Paris fined the Swiss dealer $30 million for the "concealed theft" of Picassos belonging to the artist's stepdaughter which Bouvier sold to Rybolovlev's family trust. Bouvier denied any wrongdoing.

Geiger says Bouvier could now face fraud charges in the U.S., with a case that would shed light on the opaque workings of private art transactions.

At the center of the controversy is a circa 1490-1519 painting of Christ by Leonardo da Vinci, Salvator Mundi, which the Dallas Museum of Art tried hard to acquire after the rediscovered masterpiece was authenticated. The museum did not get the da Vinci. Bouvier is reported to have sold it to Rybolovlev for $127.5 million in 2013. The Russian art collector says that he learned he'd paid about $50 million more than what the seller received, alleging that Bouvier took an overly steep commission as the middleman in the deal.