It took paramedics five minutes to restart the heart of a Taronga Zoo worker after she was pinned against a bollard by a young male elephant who shot to fame as Mr Shuffles.

Zookeeper Lucy Melo is in a critical but stable condition in Royal North Shore Hospital after the incident this morning.

Zoo keeper Lucy Melo pictured alongside elephant Tang Mo in May.

Zoo director Cameron Kerr this afternoon told media the accident occurred about 11.30am during a training exercise in which the young elephants learn to wash themselves.

Mr Kerr said 2½-year-old Asian elephant Pathi Harn pushed Ms Melo against a fence pole in the barn area of the elephant enclosure.