A reclusive centenarian heiress whose three lavish mansions sit empty while she has resided in a New York City hospital for over two decades is now the subject of an investigation by the Manhattan district attorney’s office into what has been happening with her finances.

The heiress, 104-year-old Huguette Clark, has not been seen in public for decades, according to MSNBC. The daughter of a one-term U.S. senator and copper mining magnate from Montana, Clark was born in Paris and grew up on Fifth Avenue during the Roaring 20s, where her family’s mansion was the scene of wild parties. She later inherited another New York mansion, the largest on Fifth Avenue, valued at $100 million, and owns other multi-million-dollar spreads in Connecticut and Santa Barbara.

Clark has no children, not counting the doll collection that reportedly surrounds her in her hospital room, and her estimated half-billion-dollar fortune has been overseen by an accountant and a lawyer, who are the only ones who have had contact with her besides the hospital staff. However, the accountant has reportedly had his own tax problems and run-ins with the law, including a felony conviction, and neither he nor the attorney is saying much about their client. Meanwhile, Clark’s “castle” in Connecticut, known as Le Beau Chateau, is on the market for $24 million.

The DA’s office is concerned that Clark may be another elderly heiress like the late Brooke Astor who is being taken advantage of by the professionals who are supposed to have a fiduciary duty to safeguard her interests. So far, there has been no proof that Clark’s accountant and lawyer have been fleecing her, and they may only be using her money to pay the considerable property taxes and upkeep on the residences she still owns.

But the mystery surrounding Clark has only deepened over the years since she virtually vanished from public sight, and the Manhattan DA hopes to lift the veil of secrecy.