She was smiling when she was kidnapped. Or was she?
When three men snatched the Mona Lisa from the Louvre in 1911, the theft caused panic in Paris and made headlines around the world. The painting's disappearance, and its recovery more than two years later, remains the best-known art crime in history. Yet it's far from the only one. The FBI estimates that art crimes today total as much as $6 billion a year globally, Bloomberg's Phil Mattingly reports. It's such a big problem that the FBI established an art crime unit in 2004.
Here, in ascending order by estimated value, are the FBI's top 10 art crimes under investigation. (All estimates are according to the FBI unless otherwise noted.)