BOSTON (AP) — Twenty-two historic artifacts that were looted following the Battle of Okinawa in World War II have been returned to Japan after a family from Massachusetts discovered them in their late father’s personal items, the FBI said Friday.

The 22 artifacts, some of which date back to the 18th and 19th centuries, represent a significant piece of Okinawan history. They include six portraits, a hand drawn map of Okinawa from the 19th century, and various pieces of pottery and ceramics, officials said.

The Boston division of the FBI said they helped orchestrate the return of the items, which had been missing for almost 80 years to the government of Japan, Okinawa prefecture. A formal repatriation ceremony will be held in Japan at a later date.

In 2001, the Okinawa Prefectural Board of Education registered some of the artifacts with the FBI’s National Stolen Art File, a database of art and cultural property that have been reported stolen to the FBI by law enforcement agencies in the U.S. and abroad.

The artifacts were discovered when a family, who wishes to remain anonymous, came across what appeared to be valuable Asian art in their late father’s personal effects, according the FBI.

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Their father was a World War II veteran, but never served in the Pacific Theater. The family then checked the National Stolen Art File and discovered that at least four of the items were missing 18th century portraits that had been listed in the database.

The FBI was able to authenticate the artworks.

“This case highlights the important role the public plays in recognizing and reporting possible stolen art. We’d like to thank the family from Massachusetts who did the right thing in reaching out to us and relinquishing these treasures so we could return them to the people of Okinawa,” Jodi Cohen, special agent in charge of the FBI Boston Division, said in a statement.

On Friday, Denny Tamaki, the Governor of Okinawa prefecture, announced the return of the artifacts to the people of Okinawa, Japan, according to the FBI.