After 23 years and thousands of leads, the FBI says that they know who stole 13 masterpieces from the Isabella Stewart Gardner Museum in Boston. New developments have helped investigators zero in on suspects who made off with paintings by the likes of Rembrandt, Degas, Vermeer, and Manet, valued in excess of $500 million,.

WGBH's Emily Rooney spoke with Gardner Museum director Anne Hawley and FBI special agent/art crime unit investigator Jeff Kelley for an update on the case.

Kelley said that while he has knowledge of the perpetrators, he will not announce names to the public, adding "we feel it is important to kind of lay our cards out on the table and say we know who did it, and we know who is involved, but we need your help. We still have an investigation here, and we still have to preserve the integrity of the investigation."

The largest art theft in history took place on St. Patricks Day in 1990. Two men in disguise as police officers were allowed to enter the museum after hours with no questions asked. They then handcuffed the two guards on duty and took off with some of the world's most prized paintings, including Rembrandt's only seascape and a Vermeer.

Following the heist, the museum receieved many threats, says Hawley, including bomb threats from criminals seeking attention from the FBI. Kelley says that criminals tried to extort the museum for money.

Recently, the FBI has publicly released "Most Wanted" posters for each missing artwork, a tactic that WGBH says resembles their strategy before capturing notorious mobster James "Whitey" Bulger.

A $5 million reward is offered for the art's recovery.

Kelley believes the artworks can be found, saying, "I don't know if they are still together. I think they are all in existence."