The collector, 91-year-old Donald Miller, claims he legally obtained the odd collection – ranging from shrunken heads, a sarcophagus and a Nazi helmet – from travelling the world over eight decades.
The FBI is not so sure.
With the aid of experts, the FBI will catalogue the thousands of items found on Miller’s property in Waldron, Indiana in attempt to ascertain where and if he obtained the items legally.
They could end up back in Australia, New Zealand, Papua New Guinea, China, Russia, Peru or other countries.
“We have a multi-disciplinary team of archaeologists and anthropologists who are assisting in the identification of the items,” FBI special agent Drew Northern told AAP.
“Our goal will be the repatriation of the items back to Australia, New Zealand or other countries we identify.”
The FBI has declined to identify items publicly, but Miller over the years has opened up his home to visitors, including school groups.
A 46m underground tunnel links two buildings on Miller’s property.
Agents from the FBI’s art crime unit spent Thursday loading trucks with artefacts and they expect it will take “months” to catalogue the haul.
The artefacts were well kept and in quality rival those in many top museums.
Among the most intriguing items according to visitors included: a shrunken head; Ming Dynasty jade; a skull pierced by an arrowhead spear; a Nazi helmet; a human skeleton; an 18.3m-long anaconda skin; and a chunk of concrete from the bunker where Adolf Hitler committed suicide.