The final necropsy was released Thursday for the Baton Rouge Zoo’s young Malayan tiger, Hadiah, who was found unexpectedly dead one morning a couple of weeks ago.

Despite 28 tests being performed, the tiger’s definitive cause of death is still unknown. But the report says gastric dilatation is the highly suspected reason behind Hadiah’s death.

“Gastric dilatation is what we initially suspected as the cause of death based on the video footage we had from her den, but we couldn’t say that conclusively without further testing,” said Dr. Gordon Pirie, zoo veterinarian, in a news release. “Technically the definitive cause of death is still unknown, but gastric dilatation is the most likely cause based on clinical observations and abnormalities found in the tiger’s stomach lining.”

Gastric dilation is when an animal’s stomach becomes overstretched and rotated by excessive gas. It can cause animals to have hypotension, ischemia and shock that lead to their death.

The zoo officials said the condition is unpreventable and often fatal.

All of the tests run by the Louisiana Animal Diagnostic Laboratory at the LSU School of Veterinary Medicine were negative for diseases, toxins and pathogens that could have killed the tiger.

Hadiah was almost two years old, nearly 200 pounds and a favorite attraction for zoo visitors. She lived in a habitat with her sister, Kayu Merah and mother, Nazira.

After she was found dead, zoo officials reviewed video footage that showed her resting before exhibiting obvious sings of distress, they said. She died 15 minutes after she started showing problems.

Zoo Director Phil Frost asked the U.S. Department of Agriculture to investigate the zoo after Hadiah’s death. It was one of a few high-profile animal deaths at the zoo between March and April.

Frost also asked the zoo’s accrediting agency, the Association of Zoos and Aquariums, to perform an audit after two elderly giraffes died at the zoo in one weekend.

The results of the investigation and audit are still pending.

The zoo’s assistant director Sam Winslow told the BREC Board of Commissioners last week that 18 animals have died this year on which they have performed necropsies. Many were small animals, like birds, but eight were mammals. They included an elderly cheetah, a serval with cancer, a sheep with an inoperable bladder stone and an antelope that broke its leg and was euthanized.