Estimates of the stolen works have generally been in the $500 million range, but experts caution that there is no way to reliably value such singular works. It has been called the largest art theft in U.S. history.
The bureau used the anniversary of the robbery to announce a reward - posted by the museum - and appeal to the public for help.
Richard DesLauriers, who heads the FBI's Boston office, called the robbers part of "a criminal organization based in New England the mid-Atlantic states" but didn't elaborate. He did say, however, that they believe the stolen artwork traveled through Connecticut and Philadelphia.
"But we haven't identified where the art is right now, and that's why we are asking the public for help," DesLauriers said.
Hoping to capitalize on the reach of the Internet and social media, the bureau unveiled a web page with photos, video and other information dedicated to the robbery and subsequent investigation.
"It's likely, over time, someone has seen the art hanging on a wall, placed above a mantel, or stored in an attic," said Special Agent Geoff Kelly, the Boston-based agent who heads the FBI investigation. "We want that person to call the FBI."
Among the 13 items stolen was The Concert (1658-60), one of only 36 known works by 17th-century Dutch master Jan Vermeer. The oil painting depicts two women, one at a harpsichord, the other standing alongside, completely absorbed in their imminent recital.
Three Rembrandts were taken, two paintings - The Storm on the Sea of Galilee (1633), Rembrandt's only known seascape, and A Lady and Gentleman in Black (1633), a double portrait - and an etched self-portrait of the artist.
Landscape with an Obelisk (1638), an oil long thought to be by Rembrandt, was taken from its spot opposite The Concert. In the 1980s, scholars identified the artist as Govaert Flinck, a pupil of Rembrandt's.
The Vermeer, Rembrandts and the Flinck were removed from the second floor of the museum. On the same floor, thieves helped themselves to five gouache drawings from the 1880s by Edgar Degas, all on paper.
Edouard Manet's small oil, Chez Tortoni (1878–1880), was taken from the Blue Room on the museum's first floor.
Thieves also stole two objects: a 19th-century gilt bronze eagle from atop a pole supporting a Napoleonic flag; and a Shang Dynasty bronze beaker from 1100-1200 BCE.
When museum workers arrived the next morning, they discovered the artworks gone and the security officers still handcuffed to pipes in the cellar. Empty frames hang now where once were artworks, a reminder, the museum says, of ongoing efforts to find the art and return it.
Contact John P. Martin at 215-925-2649, at email@example.com or @JPMartinInky on Twitter.