(CNN) A Ming Dynasty vase, an Italian mosaic and the bones of hundreds of Native Americans have been sitting in an Indianapolis warehouse for years. A group of FBI agents had quietly started returning them -- but they hit a snag.

They've only been able to return about 15% of the items because not enough people have come forward to claim them, FBI Special Agent Tim Carpenter said in a statement.

The artifacts, which are part of the "largest single recovery of cultural property in FBI history," were found in 2014, the FBI said in a statement.

A tip led the FBI's art crime team to a Waldron, Indiana farmhouse where thousands of artifacts from around the world and even the remains of hundreds of Native Americans were being stored.

The artifacts were found at a Waldron, Indiana farm in 2014.

Don Miller, the farm's owner, was a retired "scientist who helped build the first atomic bomb," according to the FBI. He had traveled extensively for decades, collecting the more than 42,000 items in his home.

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