ROME - The United States on Tuesday officially returned 25 artifacts looted over the decades from Italy, including Etruscan vases, 1st-century frescoes and precious books that ended up in U.S. museums, universities and private collections.

Italy has been on a campaign to recover looted artifacts, using the courts and public shaming to compel museums and collectors to return them, and has won back several important pieces.

The items returned Tuesday were either spontaneously turned over to U.S. authorities or seized by police after investigators noticed them in Christie's and Sotheby's auction catalogues, gallery listings, or as a result of customs searches, court cases or tips. One 17th-century Venetian cannon was seized by Boston border patrol agents as it was being smuggled from Egypt to the U.S. inside construction equipment, police said.

U.S. Ambassador John Phillips joined Italy's Carabinieri art police to show off the haul. It included Etruscan vases from the Toledo Museum of Art and the Minneapolis Institute of Arts, 17th-century botany books from Johns Hopkins University in Baltimore, and a manuscript from the 1500s stolen from the Turin archdiocese in 1990 that ended up listed in the University of South Florida's special collections.

"Italy is blessed with a rich cultural legacy and therefore cursed to suffer the pillaging of important cultural artifacts," Phillips said, adding that Interpol estimates the illicit trade in cultural heritage produces more than $9 billion in profits each year.

Police said several of the items were allegedly sold by Italian dealers Giacomo Medici and Gianfranco Becchina, both convicted of trafficking in plundered Roman artifacts. After the objects were recovered, Italian authorities confirmed their provenance.

Police stressed that most collectors and museums willingly gave up the artifacts after learning they had been stolen. The Minneapolis museum director contacted the Italian culture ministry after reading an article about one suspect piece, police said.

Phillips praised the collaboration between Italy's police and U.S. Homeland Security and border patrol agents. He also said the U.S. had returned more than 7,600 objects to over 30 countries and foreign citizens since 2007.