A zookeeper nearly died after being crushed against a bollard by Taronga Zoo 'miracle elephant' Mr Shuffles on Friday.

Paramedics who were called to the zoo's Asian elephant enclosure around 11:30am say the woman, in her 40s, suffered severe chest injuries and went into cardiac arrest as they battled to save her life.

The zoo says she had been crushed by two-year-old Asian elephant Pathi Harn - aka 'Mr Shuffles' - during a routine training exercise.

Her heart was stopped for five minutes before she was revived and rushed to Royal North Shore Hospital in a critical condition.

Asian elephants: Factbox Male Asian elephants can weigh more than 5 tonnes and be more than 3 metres tall.

Male Asian elephants can weigh more than 5 tonnes and be more than 3 metres tall. They are found in India, Sri Lanka, Burma, Indonesia, Thailand, Cambodia, Vietnam, Laos, Malaysia, Nepal, Bangladesh and southern China.

They are found in India, Sri Lanka, Burma, Indonesia, Thailand, Cambodia, Vietnam, Laos, Malaysia, Nepal, Bangladesh and southern China. Asian elephants live for up to 70 years.

Asian elephants live for up to 70 years. They are under threat because of habitat destruction and poaching.

They are under threat because of habitat destruction and poaching. Taronga has 10 Asian elephants.

Taronga has 10 Asian elephants. Australia's first captive-born elephant calf, Luk Chaim was born at the zoo in July 2009.

"When ambulance crews arrived the patient was conscious and talking to them," ambulance service spokesman Andrew Wood said.

"She did briefly say what has happened. The patient then went into cardiac arrest. A second paramedic crew was called. The crew worked on the female zoo worker and got her heart beating again."

Pathi Harn was hailed as the zoo's 'miracle elephant' in March 2010 when he was born alive after it was believed he was dead in his mother's womb.

Initially christened 'Mr Shuffles' by delighted zoo staff, the elephant was renamed Pathi Harn - Thai for "miracle" - later that month.

Sorry, this video has expired Taronga Zoo CEO Cameron Kerr launches investigation

Zoo director Cameron Kerr said the injured keeper had worked with Pathi Harn since the elephant's birth.

He said the zoo had launched a full investigation into the incident.

"I can ensure you Taronga's elephant programs are world standard," Mr Kerr told reporters.

"We're very worried about the keeper. I don't want to be speculating about things.

"These animals are what we call domestic elephants. These are termed domestic elephants, because they come from families – [are] brought up with people," he added.

"There's a very close bond between our staff and our animals.

"Our keepers did act immediately when they saw the incident was going on – they moved the calf away from the keeper that was injured and called the ambulance service," he added.

"There was never any risk to the public, and nor is there now."

Sorry, this video has expired Flashback: Mr Shuffles gets a miracle name

The zoo recently introduced three Asian elephant calves to its breeding program and keeps 10 Asian elephants in total.

On its website, the zoo says that all its elephants take part in a training program to improve their "physical and mental wellbeing".

The training involves sessions with zookeepers to teach the elephant how to respond to basic commands.

The zoo says the training also helps the elephants bring positive relationships with humans.

Zoologist Professor Roger Short, from Melbourne University, says it is unusual for a young elephant to be involved in an incident of this kind.

"It's very unfortunate and an unexpected event," he told ABC News Online.

"At least he would have had no tusks, he probably thought he was just being playful.

"Still, it's very young to be causing any problem."