Tilly Bayntun, 14, was last seen in Essex on 20 November and following extensive enquiries it is now believed that the teenager may be in Kent.
Tilly is believed to be wearing a black Nike padded style jacket with black leggings and black and grey trainers.
She is described as white, five feet five inches tall, of slim build with long straight black hair and brown eyes.
Tilly is believed to have connections in Thanet, Medway, South East London and Essex, and officers are growing increasingly concerned for her welfare.
Anyone with information as to Tilly’s whereabouts are asked to call Kent Police on 101 quoting 03-0869.