SeaWorld San Diego's youngest orca has died from a sudden illness

• Amaya, a 6-year-old orca, died suddenly at SeaWorld San Diego on Thursday.
• On Wednesday, the orca showed signs of an undisclosed illness, and veterinarians began treating her.
• About 24 hours later, she died. The cause of death is unknown and experts are conducting a post-mortem exam.

The youngest orca at SeaWorld San Diego died from an undisclosed illness on Thursday, the animal theme park told Insider in a statement.

SeaWorld said that 6-year-old Amaya first started showing signs of illness on Wednesday and her condition "continued to decline rapidly."

Animal-care experts and veterinarians began treating Amaya on Wednesday; on Thursday the orca died, SeaWorld said in its statement.

"Her death was sudden and unexpected," the park told Insider.

While the exact cause of death is still unknown, SeaWorld is conducting a post-mortem exam. The park said that it may take several weeks for the exam's results.

"This is a very difficult time for those who knew and loved Amaya," SeaWorld said in its statement. "The specialists who cared for her at SeaWorld are heartbroken."

Amaya was born on December 2, 2015, and lived with her mother, Kalia, and her father, Ulises, at the park. According to SeaWorld San Diego's website, Amaya helped SeaWorld "gather and share critical information about calf development for researchers studying wild populations."

SeaWorld San Diego now has nine orcas in its care.

In 2016, the park announced it was immediately ending its orca breeding program. The current population of orcas at its three US parks will be the last generation of mammals in SeaWorld's care.

The news followed criticism and declining visitors numbers after the 2013 documentary film "Blackfish" premiered. The film told the story of Tilikum, a SeaWorld whale held in captivity, who was involved in the deaths of several people.