MIAMI (AP) — Lolita, an orca whale held captive for more than a half-century, died from old age and multiple chronic illnesses, according to a report released Tuesday by the Miami Seaquarium.

Lolita — also known as Tokitae, or Toki — died Aug. 18 at the age of 57. Her carcass was transported to the University of Georgia, where a necropsy was completed the next day. The Seaquarium released an executive summary of her necropsy Tuesday to the Miami Herald.

The exam supported early reports from the Seaquarium, which cited kidney failure as the cause of death. The veterinarian who conducted the necropsy found that Lolita suffered from acute and chronic bronchointerstitial pneumonia and renal degeneration, as well a chronic condition of the heart implying the degeneration of the cardiac valves.

Animal rights activists had been fighting for years to have Lolita freed from her tank at the Seaquarium. The park’s relatively new owner, The Dolphin Company, and the nonprofit Friends of Toki announced a plan in March to possibly move her to a natural sea pen in the Pacific Northwest, with the financial backing of Indianapolis Colts owner Jim Irsay.

Lolita retired from performing last spring as a condition of the park’s new exhibitor’s license with the U.S. Department of Agriculture. She had not been publicly displayed since. In recent months, new upgrades had been installed to better filter the pool and regulate her water temperature.

Federal and state regulators would have had to approve any plan to move Lolita, and that could have taken months or years. The 5,000-pound (2,267-kilogram) orca had been living for years in a tank that measures 80 feet by 35 feet (24 meters by 11 meters) and is 20 feet (6 meters) deep.