Nearly two dozen stolen artifacts were recently returned to Japan after a Massachusetts family discovered the looted art while cleaning out their late father's attic.

The family - which was not identified publicly - found 22 artifacts, dating back to the 18th century and originally from Okinawa. The pieces included pottery, painted scrolls and a hand-drawn map of Okinawa, according to the Federal Bureau of Investigation's Art Crime team.

"When taken together, they really represent a substantial piece of Okinawan history," said Special Agent Geoffrey J. Kelly of the FBI Boston Field Office.

The artifacts were accompanied by a letter confirming that they were taken from Okinawa in the final days of World War II. The family's father had served in World War II but not in the Pacific Theatre. 

"They came across some of what appeared to be very valuable Asian art," Kelly said.

"They looked old and valuable. And because of this, they did a little research and they determined that at least the scrolls had been entered about 20 years ago in the FBI's National Stolen Art File."

The FBI worked with the Smithsonian Institution's National Museum of Asian Art in Washington, D.C., to prepare the art pieces for travel back to Japan. The pieces were officially handed over to Okinawa officials on March 15, but there will be a formal repatriation ceremony at a later date.

"A nation's cultural identity is really summed up in the artifacts and the history," said Kelly, explaining the significance of the repatriation.

"And without it, you're taking away their history. And the surest way to eliminate a culture is to eliminate their past. And so, it's really important for us as stewards of artifacts and cultural patrimony to make every effort that we can to see that these go back to the civilizations and the cultures in the countries where they belong."