FILE - In this March 11, 2010 file photo, the empty frame, center, from which thieves cut Rembrandt's "Storm on the Sea of Galilee" remains on display at the Isabella Stewart Gardner Museum in Boston.... (Associated Press) 
 
 FILE - This undated file photograph provided by the Isabella Stewart Gardner Museum shows the painting "Chez Tortoni," by Edouard Manet, one of more than a dozen works of art stolen in the early hours... (Associated Press) 
 
 FILE - In this March 21, 1990 file photo, a security guard stands outside the Dutch Room of the Isabella Stewart Gardner Museum in Boston, where robbers stole more than a dozen works of art by Rembrandt,... (Associated Press) 
 
 In this March 18, 1990 still image from surveillance video released by the U.S. Attorney's Office,Thursday, Aug. 6, 2015, an unauthorized visitor walks inside the rear entrance of the Isabella Stewart... (Associated Press) 
 
 Authorities hope the never-before seen video will spark leads to help recover the 13 pieces of stolen artwork, worth at least $500 million. The video footage, taken by the museum’s surveillance cameras and recently examined by investigators, shows the night watchman open the museum’s side door and grant unauthorized access to the man at about 12:49 a.m. on March 17, 1990 — 24 hours before the museum was robbed by two men dressed as police officers who arrived at the same door. It was not immediately clear why the surveillance footage of the night before the robbery had not been made public before, and whether it was viewed by the FBI in the initial investigation. The robbers had seized surveillance footage from the night of the heist, though they did not take footage from the previous night. Several law enforcement officials said the video appears to have been overlooked and mixed in with other evidence at the onset of the case. US Attorney Carmen M. Ortiz said that a team of investigators began reviewing the original evidence, and that one of them, Assistant US Attorney Robert Fisher, requested the video, which was in the custody of the FBI. By releasing this video, we hope to generate meaningful leads and ultimately recover the stolen artwork.” 
 
 A $5 million reward has been offered by the Museum for information that leads directly to the recovery of all of the stolen items in good condition. Authorities have repeatedly said on March 18, 1990, two white men dressed in Boston police uniforms gained entrance to the museum by telling the security guard at the watch desk that they were responding to a report of a disturbance. The color, make, and model of the car in the new surveillance video could not be determined, though authorities said Thursday that it matches the general description of the vehicle seen the night of the robbery.
– The FBI hopes new surveillance footage released today will aid in the recovery of 13 priceless artworks stolen 25 years ago and help put to rest one of Boston's greatest mysteries. In the early hours of March 18, 1990, two men dressed as cops were let into the Gardner Museum, where they tied up two security guards and absconded with the artwork and the museum's security footage, the Boston Globe reports. But the thieves, who have never been identified, may have missed one key thing. According to the FBI, surveillance footage from the day before the robbery shows a security guard letting a man into the museum—against protocol—through the same door later used in the robbery. The Globe reports it's unclear why this footage wasn't viewed by law enforcement earlier, but it could show a "dry run" of the heist. The newspaper identifies Richard Abath as the security guard in the footage, and the FBI is hoping the public can help identify the mystery man he lets in. Abath, a rock musician at the time who now lives in Vermont, has claimed he had no part in the robbery, but this new footage appears to contradict a number of his statements. No one has ever been charged with stealing the art—for which there is a $5 million reward—and no one ever will, as the statute of limitations has expired. Someone in possession of the paintings, however, could face charges. Their total value exceeds $500 million, reports AP.