Shelley Pratt vanished on the way home from school five weeks ago.
She was last seen talking to an unknown man.
She was still in school -trousers and a purple hooded top with an I Love London slogan.
After talking to the mystery man, who also approached other women in the centre of Croydon, South London, -her Oyster travel card was used on another bus.
Shelley is described as 5ft 7in, brown haired.
She's had absolutely no contact with friends or family since her disappearance and it is possible that she may be with someone, perhaps in a house or a flat.
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The women were reportedly both students at City and Islington College campus in Holloway Road.