Desteny Sturgess Green, aged 14, is missing from the Womersley area of North Yorkshire.
The last sighting of the youngster was at 6.50am yesterday at the Jet Garage on Selby Road in Askern, Doncaster.
North Yorkshire Police said: “Police are currently carrying out enquiries to locate her but are growing increasingly concerned for her welfare and are now treating her as a high-risk missing person.”
Desteny was last seen wearing a grey hoodie, black trousers, Nike trainers and she was carrying a black bag.
She is approximately 5ft 5ins tall, slim and she has long, straight, brown hair.
Desteny has links to West Yorkshire, South Yorkshire and Derbyshire.
Anyone who has seen her, or has information that could assist us, is asked to call 101.
Any sightings should be reported immediately by calling 999 and quoting reference number 12220038265.