A female zookeeper was attacked and killed by a male Sumatran tiger on Sunday while the zoo remained opened to visitors in Hamilton, New Zealand, according to The Associated Press.

Police said they received a call from the Hamilton Zoo at approximately 11 a.m. about a female zookeeper who had been mauled to death by one of the five tigers at the zoo.

The zoo, owned by Hamilton City Council, asked the visitors to leave and said it would remain closed until Thursday as authorities investigate to determine what exactly happened.

"We are deeply saddened to confirm the death of a female staff member today after an attack by one of the zoo's Sumatran tigers," Hamilton City Council said in a statement posted on its website.

One of the zoo's visitors, Adam Rich, said he saw the tigers Sunday morning and noticed a female zookeeper opening up a gate in order to give the animals access to the outdoor section of the enclosure.

He said about 45 minutes later, zoo officials approached him and asked him to leave. They were offering refunds to everyone, he added.

"They seemed a bit panicky," he said, according to The New Zealand Herald. "I thought an animal had escaped but they guaranteed that an animal did not escape."

Jeff Neems, spokesman for the Hamilton City Council, said that the tiger who killed the woman is named Oz and is the only adult male tiger in the zoo.

He said the visitors were never in any danger, at any point of time during the incident and that all the animals were safely contained in their enclosures.

"Our focus at this time is on providing the adequate support for our staff and family members who have been affected by this tragic incident," Neems added. 

In a similar incident, a Sumatran tiger attacked and killed a zookeeper during a routine cleaning of its enclosure at a Polish zoo last week, as HNGN previously reported.