DETROIT (AP).- The St. Louis Art Museum has filed a federal lawsuit to try to keep a 3,200-year-old mummy mask that Egypt wants returned, claiming it was stolen nearly two decades ago. The museum claims the U.S. government is trying to seize the 20-inch-long funeral mask of Ka-Nefer-Nefer and return it to Egypt. But the museum says it has legal rights to the mask it purchased from a New York art dealer for $499,000 in 1998. Egypt officials have claimed the mask was stolen in the early 1990s from a storage room near a pyramid. The suit, filed in federal court in St. Louis on Tuesday, claims there is no proof the mask was stolen. It also claims that the statute of limitations has expired for any seizure.