Boston’s Isabella Stewart Gardner Museum is offering the sum for information leading to the return of 13 pictures seized from the museum in 1990.
The works taken in a robbery on March 18, 1990 include Vermeer’s painting The Concert, Rembrandt’s Christ in the Storm on the Sea of Galilee and A Lady and Gentleman in Black, Édouard Manet’s Chez Tortoni, and Edgar Degas’ Leaving the Paddock.
It remains the largest art heist in history with more than $500m of artworks taken.
Steve Kidder, president of the Gardner Museum’s board, said: “It is our fervent hope that by increasing the reward, our resolve is clear that we want the safe return of the works to their rightful place and back in public view.”
Security director Anthony Amore said: “Typically, stolen masterpieces are either recovered soon after a theft or a generation later. We remain optimistic that these works will ultimately be recovered.”
The reward will be offered until December 2017.
Anyone with information should contact Anthony Amore by calling 00 1 617 278 5114 or email theft@gardnermuseum.org.