Twenty three years ago today, thieves pulled off one of the greatest art heists in history – making off with $500 million worth of art from the Isabella Stewart Gardner Museum. Today, the FBI announced that it had finally figured out the identities of at least two of the people involved in the heist.

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The Boston Globe writes:

“The FBI believes with a high degree of confidence in the years after the theft the art was transported to Connecticut and the Philadelphia region and some of the art was taken to Philly where it was offered for sale by those responsible for the theft. With that confidence, we have identified the thieves, who are members of a criminal organization with a base in the mid-Atlantic states and New England,” Richard Deslauriers, the special agent in charge of the Boston office of the FBI said in a statement.

The heist was a sensation in the art world, and at least one book has been written about it. Here’s how the website of Ulrich Boser, author of The Gardner Heist, summarizes what happened:

Shortly after midnight on March 18, 1990, two men dressed as police officers broke into the Isabella Stewart Gardner Museum in Boston and stole 13 masterpieces including five Degas, three Rembrandts, and a Vermeer. The plundered works are worth an estimated $500 million, and the theft remains the largest unsolved art heist in history. Detective Harold Smith worked the theft for years, and after his death, reporter Ulrich Boser decided to pick up where he left off. Traveling deep into the art underworld, Boser explored Smith’s unfinished leads and came across a remarkable cast of characters, including the brilliant rock ‘n’ roll art thief; the golden-boy gangster who professes his innocence in rhyming verse; and the Boston heiress Isabella Stewart Gardner, who stipulated in her will that nothing should ever be changed in her museum.

The thieves made off with the following works of art, 13 in total, according to the FBI files:

While the FBI now thinks it knows at least two of the criminals responsible, it’s not totally sure where the art itself went. They think it was sold about ten years ago, but since then have lost track of where the individual pieces might be. The Boston Globe writes:

“Unfortunately, we haven’t identified where they are right now and that’s why we are coming to the public for their help,” Geoff Kelly, the special agent who spearheaded the investigation in the Boston office, said in a statement. The FBI said that it was continuing its search both in and beyond the Connecticut and Philadelphia areas and launching a public awareness campaign that would include outreach through both billboards and the Internet.

In the meantime, they’re hoping that the two suspects—whose names they haven’t released yet—might provide information about where the art went, and who else might have been involved.

More from Smithsonian.com:

Meet Ulrich Boser, Author of The Gardner Heist, from Smithsonian Books