A popular big cat at Zion Wildlife Gardens has died.
Barbary lioness Shia died in her enclosure on Friday from what staff believe were natural causes.
Results of an autopsy, expected to be released tomorrow,  will reveal the cause of death.
Shia was born in 1999 and, with her brother Zion, was handraised originally in Zion Wildlife Gardens in Kerikeri before moving to Whangarei.
Zion Wildlife Gardens spokeswoman Sara Reid said Shia was found unwell while one of the guides was taking a school tour around the park about 10.30am.
Ms Reid said the group was moved on from the area and staff were called to attend to the sick cat.
Due to new regulations imposed after the death of big-cat handler Dalu Mncube last year, staff had to lock away the other lion, Zion, in the enclosure before they could go to the aid of Shia.
By that time, Shia had died. She was removed and vets were called for an autopsy.
"The guys had cleaned the enclosure and fed the lions in the morning and there was nothing untoward or anything to indicate she was unwell," Mrs Reid said.
"Some of the staff have known Shia for 10 years, so for them it's like losing a family member."
A Whangarei woman was with her son during a school visit to the park on Friday.
She did not want to be identified but said near the end of the tour she noticed the lioness lying very still on the ground.
"At first look the kids thought she was dead. We had a closer look to see if her chest was moving but she definitely wasn't breathing."

 Shia and Zion had lived together for her whole life.
Shia was the submissive sister when it came to food time, always allowing Zion to eat first.
Most days the lioness could be found sunbathing with her paw resting across Zion's side or the two of them stretched out side by side on their favourite rock.
The two featured in a popular television advertisement for Sky and were filmed sitting on a couch watching a wildlife programme.
Shia will be buried in an area dedicated as a cemetery for big cats on the property.