Police investigating an apparent gang rape in Sydney's northern suburbs have found that the incident did not occur.

A 17-year-old girl told police that she was abducted from Merindah Street in Baulkham Hills after leaving a house party in the early hours of March 3.

She said a group of five men in a green-coloured sedan asked her for directions to a nearby shopping centre before dragging her into the car, driving her around for several hours and raping her several times.

She told police she was then dumped on a Castle Hill Street where she made a panicked phone call to a relative.

Police circulated a rough description of one of the men and launched Strike Force Mikkelsen comprising local detectives and Sex Crimes Squad investigators.