FBI confident they know who carried out famed 23-year-old $500-million art heist, offers reward Gardner Museum via Reuters Govaert Flinck's "Landscape with an Obelisk" (1638) is one of 13 works of art stolen from Boston's Isabella Stewart Gardner Museum in a brazen robbery on March 18, 1990. By Pete Williams, Justice Correspondent, and Andrew Mach, Staff Writer, NBC News Who is behind the largest art heist in world history? After an aggressive 23-year investigation that included law enforcement tracking down and following leads around the globe, the FBI on Monday said officials believe they know who famously made off with 13 works of art from Boston's Isabella Stewart Gardner Museum in 1990, valued collectively at more than $500 million. But today, instead of making arrests, the FBI, along with the museum and the U.S. Attorney's Office for the District of Massachusetts, is making a plea: bring back the artworks and federal prosecutors will consider not filing charges. Plus there's a $5 million reward. "The FBI believes with a high degree of confidence that in the years after the theft, the art was transported to Connecticut and the Philadelphia region, and some of the art was taken to Philadelphia, where it was offered for sale by those responsible for the theft," Richard DesLauriers, a special agent in charge of the FBI's Boston office said Monday. With that same confidence, we have identified the thieves, who are members of a criminal organization with a base in the Mid-Atlantic states and New England. But we haven't identified where the art is right now, and that's why we are asking the public for help. In what is one of the FBI's Top Ten Art Crimes, two men disguised as policemen allegedly entered the museum during the early morning hours of March 18, 1990, overpowered the security guards and pilfered 11 paintings and drawings, some of which were cut from their frames and rolled up, and two sculptures, including a 3,000-year-old Chinese bronze vessel. See the paintings that were stolen in this gallery from the FBI. The guards, who were not to let any outsiders in, were found handcuffed and duct-taped to chairs in the basement of the museum seven hours later. No one has ever been arrested. Rembrandt's "Storm on the Sea of Galilee The haul, which included three works by Rembrandt, a painting by Dutch painter Vermeer, a Manet painting and five drawings by Degas, was the largest private property theft ever, Harvard Magazine reported. Several empty frames still hang in the museum's Dutch Room gallery, both as an homage to the missing works and as placeholders for when they are returned. With these considerable developments in the investigation over the last couple of years, it's likely over time someone has seen the art hanging on a wall, placed above a mantel, or stored in an attic. We want that person to call the FBI." said Special Agent Geoff Kelly, who heads the FBI investigation. The statutes of limitation have long since passed for prosecuting the the thieves, though the government could still bring charges of receiving stolen property. But the FBI and the Justice Department believe the most important goal now is recovery, not prosecution. "With this announcement, we want to widen the "aperture of awareness" of this crime to the reach the American public and others around the world," DesLaurier said. The successful return of the paintings to the Gardner Museum would be the final chapter in one of the most significant art theft cases in the FBI's history. And it is a result we would all welcome - seeing these paintings returned to their rightful home. "It's time for these paintings to come home," said Anthony Amore, the museum's chief of security. You don't have to hand us the paintings to be eligible for the reward. We hope that through this media campaign, people will see how earnest we are in our attempts to pay this reward and make our institution whole. The $5 million reward is not from the federal government. It was raised by the museum from private donors. To recover stolen items and prosecute art and cultural property crime, the FBI has a specialized Art Crime Team of 14 special agents supported by special trial attorneys. The team investigates theft, fraud, looting, and trafficking across state and international lines, with estimated losses running as high as $6 billion annually. The FBI also runs the National Stolen Art File, a computerized index of stolen art and cultural properties that is used as a reference by law enforcement agencies worldwide. The Gardner Museum was founded by Isabella Stewart Gardner, an art collector who died in 1924. Her will contained very particular conditions on the running of the museum, including the arrangement of her collection and free admission to anyone named Isabella, a practice that continues today. March 19, 1990: The Gardner Museum in Boston was the target of what turned out to be the largest art heist in history. It was pulled off with shocking simplicity. Two men dressed as policemen walked in, then walked off with numerous masterpieces. NBC's Tom Brokaw and Fred Briggs report.