Cairo, Egypt ? More than half a century ago, a prominent Egyptian archaeologist unearthed a stunning ancient mummy mask at the Saqqara pyramids near Cairo — the golden image of a noblewoman’s face.

Mohammed Zakaria Ghoneim deposited the 3,200-year-old relic in a warehouse at Saqqara, where he meticulously documented his discovery. Seven years later, in 1959, Egyptian records show it was still in the same storeroom.

What happened to the burial mask of Ka Nefer Nefer in the four decades that followed is a mystery.

It resurfaced in 1998 when the St. Louis Art Museum acquired it. And now it is at the center of one of the most acrimonious fights in the antiquities world.

The case lays bare the complexities involved in growing efforts by Egypt and other countries to reclaim artifacts stolen or looted from their ancient civilizations.

Local and international laws are often inadequate or nonexistent. The process requires delicate cooperation between government, law enforcement, museums, and antiquities dealers. And frequently, there are gaps in the historical records.

Claims are attracting increasing attention after prestigious institutions such as the J. Paul Getty Museum of Art in Los Angeles and the Metropolitan Museum of Art in New York agreed to return looted or stolen artwork or antiquities. Zahi Hawass, head of Egypt’s antiquities authority, said his country has recovered some 5,000 stolen artifacts since 2002, and is pursuing dozens more.

“This is the No. 1 case,” he told The Associated Press in an interview. “Egypt has a right to the mask.”

Hawass said there is no record showing the mask ever left Egypt legally. But the St. Louis museum contends Egypt has not proven it was stolen.

“That is a charge we took very seriously,” museum director Brent Benjamin told the AP. “If that is true, there is no question that the museum would return the object,” he said.

“To date, we have not seen information that we believe is compelling enough to return the object.”

After a recent request from Hawass, who does not shy away from using political pressure to get what he wants, the U.S. Department of Homeland Security is looking into the case.

Egyptian records seen by the AP show the burial cover for Ka Nefer Nefer’s mummy was discovered in 1952 by Ghoneim, who oversaw excavations at the Saqqara pyramids, about 12 miles south of the more famous Great Pyramids of Giza.