Although keepers are never supposed to be in the same space as the tigers, they found themselves together in the outdoor habitat that morning for reasons under investigation.
"There's some sort of error that occurred here," said Brendan Wiley, the zoo's director, told a news conference. He confirmed that several visitors to the zoo had witnessed the attack.
The employee is the zoo's primary tiger keeper and had worked there for years, according to Mr Wiley, who noted that part of her job is to clean and maintain the enclosure. He said that the keeper was in stable condition and that the zoo was reviewing its safety protocols.
The zookeeper, whom Mr Wiley declined to name, citing her family's need for privacy, suffered "lacerations and punctures" to the back of the head, neck, back and arm. She was awake and alert when she was transported to a hospital.
The attack occurred about 9:15 am and the zoo's safety protocols immediately went into effect, Mr Wiley said. A radio call alerted the staff that there was an emergency, and the zoo called 911. Nearby staff members responded to the scene to secure the tigers, and an official made the decision to temporarily close the zoo. A firearms response team also was dispatched to the tiger exhibit, but zookeepers had successfully lured the tiger away by the time it arrived.
"Some of our staff witnessed some things that you hope you go through a career without witnessing," Mr Wiley said.
The zoo has two adult Sumatran tigers: Jingga, a female, and Sanjiv, who was brought to the zoo in August 2017. Shanna Simpson, animal care supervisor, told the Topeka Capital-Journal then that Sanjiv "is the sweetest cat I have ever met."
In October, Jingga gave birth to four cubs - three males and one female.
The Topeka Zoo allowed Jingga and her cubs back into their enclosures Saturday afternoon, but Sanjiv would remain in holding overnight, Mr Wiley said.
City spokeswoman Molly Hadfield said in an email that "nothing will happen to the tiger; he is a wild animal and was acting on instinct."
Sanjiv is too valuable to conservation efforts to euthanise. Sumatran tigers are critically endangered, and only about 400 remain in the wild, according to the World Wildlife Fund. They are native to Indonesia, where deforestation, human encroachment and poaching have whittled their numbers to the brink of extinction.
Some zoos participate in Sumatran tiger conservation programs designed to save the species, but these efforts are not always successful. In February, a male tiger brought to the London Zoo to mate attacked and killed its prospective female partner.
The Washington Post