The 18-year-old has dislocated her left ankle at a site about 700m up the escarpment, west of the landmark.

NSW Ambulance paramedics were called just after 11.20am Tuesday.

Paramedics are now at the girl's side, but have indicated they face an "extremely difficult" job in getting her out.

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They are awaiting specicalist officers to craft what is expected to be a lengthy extraction operation.

Firefighters are also en route.

Update, 12.42pm: Rescuers are about to bring in SES volunteers to assist. Crews are accessing the site from the railway side, using a track off Clifton School Parade.

1.10pm: Rescuers will use a stretcher and a 4WD to carry the girl out. A rescue chopper flew overhead a short time ago, but is not required.

1.50pm: The girl has been collected in an ambulance.

The bridge has been a popular spot for tourists and Instagrammers since it opened in December 2005.

Visitors have found their way to vantage points on the cliff face, but none of these locations are open to the public and none feature fencing to protect people from falling.

In September 2018 a 24-year-old western Sydney man died in a cliff fall while sight-seeing at the site.

The man was walking with friends along the top of the cliff at the area where the bridge crosses over the water at the southbound end. He sat down on loose gravel on the clifftop and slipped 20 metres to the cliff's edge before plunging 40 metres to his death.

More to come.

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