It’s one of the biggest and most mysterious cases of art theft of all time, but the FBI think they might just have solved the question of who took $500 million worth of the stuff from Boston’s Isabella Stewart Gardner Museum in 1990. In a further twist though, they’re withholding the identity of the thieves.

The theft took place on March 18, 2013, and on the anniversary a new press campaign has come out, with a switch from finding out who it was who stole the artwork to finding out where it’s gone. "The key goal here is to recover those paintings and bring them back," US Attorney Carmen Ortiz said at a news conference at the FBI's Boston headquarters.

The FBI's Richard DesLauriers says the agency think that the thieves belonged to a criminal organisation based in New England and the mid-Atlantic states. It’s believed that the art was taken to Connecticut and Philadelphia after the theft, being offered for sale in Philadelphia about a decade ago. However they do not know what then happened to the art after that sale. Paintings that were included in the heist include The Concert by Johannes Vermeer; and three Rembrandts, A Lady and Gentleman in Black, Self-Portrait and Storm on the Sea of Galilee, his only seascape. The frames of all hang in the art gallery still.