NSW police puzzled by sex slave case

Police admit they're "not very close at all" to finding the Sydney unit where a 17-year-old West African girl was reportedly held for weeks as a sex slave.

The girl from Guinea says she met a man in her home country in January who offered to bring her to Australia as his cleaner and in April they travelled together via Paris to Sydney.

NSW and federal police on Friday said she was driven to a home believed to be in the city's metropolitan area - where she was kept in a room and sexually assaulted by a number of men including the African man who travelled with her.

In the early hours of April 27, the girl managed to escape and flag down a good Samaritan in a small red car who took her to an inner west asylum seeker centre.

But three weeks on police are still stumped as to where the girl was held captive and by whom.

"This has been a very very difficult investigation," Detective Acting Superintendent Mick Haddow of the sex crimes squad said on Friday.

"The statement (from the teen) has taken days and days and days to complete.

"It's really vague descriptions about units and ... we don't know what suburb we're talking about at this stage."

Police are desperately trying to track down the good Samaritan - a woman believed called Nicole - to help fill in gaps in the story.

'She's a really important witness," Supt Haddow said.

"She's also potentially a really important source of information for us in terms of identifying a crime scene."

The AFP's human trafficking unit has been brought in to investigate along with the NSW Police State Crime Command's sex crimes squad.

But they haven't been able to confirm how or when the teen entered Australia.

Supt Haddow said he can only imagine the girl's distress.

"It's a very traumatic situation ... to get over something like this can take forever," he said.

She remains in Sydney in the care of Family and Community Services.

© AAP 2017

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