Story highlights Zookeeper crushed after elephant pins her to post in Australian zoo

Taronga Zoo investigating why the elephant "challenged the keeper"

Calf involved was known as the "miracle" elephant born in 2010

The Asian elephant was conceived as part of the zoo's breeding program

A female zookeeper was seriously injured Friday after being "pinned" to a post by a young male Asian elephant during a routine training session at Sydney's Taronga Zoo.

Two other keepers rushed to the woman's aid after they heard her cries and moved the elephant away, the zoo said in a statement.

The woman was taken to hospital in a critical condition, but is now stable in intensive care. She has not been identified out of respect for her family's privacy, the zoo said.

The elephant involved was a two-and-half-year-old male calf called Pathi Harn, which means "miracle" in Thai. The calf was given the name after being born alive, even after experts pronounced him dead in the womb following a difficult eight-day labor.

The calf -- initially referred to as "Mr Shuffles" due to his odd gait -- was conceived by artificial insemination as part of the zoo's elephant breeding and conservation program.

At the time of his birth in March 2010, the young male weighed 116 kilograms and one year later tipped the scales at just over 500kgs.

The zoo said it doesn't know what provoked the calf. "It's unknown at this time why the young elephant challenged the keeper. The public were not at risk at any time and the elephants are now in their paddock at the zoo."

WorkCover, a New South Wales government agency "promoting productive, healthy and safe workplaces," is investigating the incident.

"Initial enquiries indicate that the zoo keeper suffered serious crush injuries while working in the elephant enclosure," the agency said in a press release.

The Sydney zoo is home to eight elephants, some of whom have rehabilitated from domestic elephant camps in Thailand.

According to the zoo's website , their enclosure includes deep and shallow swimming pools, mud wallows, sleeping mounds, shaded areas, scratching posts and logs.

Every morning, "the elephants and keepers walk around the exhibit paddocks and in the Zoo grounds for exercise and physical activity," the website said.

It added: "A scientific study conducted during 2006-2007 found that Taronga Zoo's elephants had an activity profile that closely matched behaviors, exercise and foraging activities of wild elephants."