(CNN) Kayla, one of SeaWorld's oldest remaining orcas, has died after first showing "signs of discomfort" two days earlier, the chain of animal theme parks said.
The 30-year-old female orca died Monday morning, with animal care specialists by her side, SeaWorld said in a statement.
"The exact cause of death will not be known until the results of a post-mortem examination are complete, which may take several weeks," it said. "The entire SeaWorld family is deeply saddened by the loss."
Kayla had no major health concerns but first showed signs of an issue Saturday afternoon, and her condition worsened over the next two days, SeaWorld said. It described Kayla a couple years ago as a "graceful, intelligent, athletic" orca.
An animal care specialist and veterinarians tried to help the orca recover, but she died at about 12:15 a.m. Monday at SeaWorld Orlando.
"While this is very difficult for all of us at SeaWorld, Kayla inspired generations of guests and employees to care and learn more about this amazing species," the organization said.
Across its three parks, SeaWorld has 20 orcas, also known as killer whales, remaining, according to its statement. After Kayla's death, SeaWorld Orlando has five, including three females and two males.
The death comes several years after SeaWorld announced it was ending its orca breeding program amid criticism about how it treated the orcas in captivity. The 2013 CNN documentary film "Blackfish" highlighted the issue, telling the story of a SeaWorld trainer killed by the 12,000-pound orca Tilikum in 2010.
The orcas in SeaWorld's care are the last generation of the mammals to be enclosed at the water parks, the company said in 2016. SeaWorld said it was moving away from theatrical killer whale shows and moving toward educational programs.