BOSTON – Twenty-five years after the famed art heist at Boston’s Isabella Stewart Gardner Museum, law enforcement officials released new surveillance video Thursday showing an unauthorized visitor entering the museum the night before the robbery.

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 low-resolution video shows a security guard appearing to hit an intercom button, then to grant access to a man who can be seen in the museum’s reception area at about 12:49 a.m. on March 17, 1990, nearly exactly 24 hours before the heist.

The man is also seen getting out of a car matching the general description of one reported to be parked outside the museum minutes before the theft. He uses the same rear entrance as the thieves, according to the office of U.S. Attorney Carmen Ortiz, which released the video.

The stolen artwork includes Vermeer’s “The Concert” and Rembrandt’s “The Storm on the Sea of Galilee.”

Ortiz’s office did not immediately respond to questions about why the video footage – captured by museum security cameras – was not released earlier.

“Over many months we have engaged in an exhaustive re-examination of the original evidence in this case. Our aim has been to ensure that all avenues have been explored in the continuing quest to recover these artworks,” Ortiz said in a prepared statement.

Ortiz said officials are hoping the public may be able to help authorities identify the unauthorized visitor or the car seen in the video.

“With the public’s help, we may be able to develop new information that could lead to the recovery of these invaluable works of art,” she said.

A $5 million reward has been offered by the museum for information that leads to the recovery of the stolen artwork in good condition.

“We remain committed to one goal: the return of all 13 works to their rightful place, which is here at the Isabella Stewart Gardner Museum,” said Anthony Amore, Director of Security at the Gardner Museum.

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.

Against museum policy, the guard allowed the men into the museum. The thieves handcuffed the museum’s two guards on duty and put them in separate areas of the museum’s basement.

No weapons were seen during the robbery and no panic button was activated. The video surveillance footage from the night of the robbery was taken by the thieves.

No one has ever been charged in the heist.