Officers are appealing for information to help trace missing schoolgirl Tilly Rawling.
The 15--year-old of Lavender Close in Attleborough was last seen at 8am on Sunday.
Her father, Matthew Rawling, first realised his daughter was missing when her sister went into her bedroom on Sunday morning to ask if she wanted pancakes and noticed the window was open.
The family then mounted an extensive search for the Old Buckenham High School pupil, driving around the Attleborough area in a bid to find her and contacting her friends to see if there had been any sightings.
Friends and the wider community have rallied round, with thousands of people sharing an appeal poster on social media and taxi drivers distributing leaflets.
Tilly called her family from a telephone number beginning in 028 at about 7.20am on Monday but the line went dead when her dad asked if someone was with her.
After calling the number back repeatedly, the family discovered the call was made from a telephone box in Hammersmith, London.
Tilly is described as being 5ft 7in tall of a slim build with waist length wavy blonde / mousey coloured hair. At the time of going missing it is believed she was wearing a black beanie hat, a hooded top, black jeans and black boots.
It is believed she might be in the London, Edinburgh or Norwich areas.
Officers are becoming increasingly concerned for Tilly's welfare and are asking anyone who may have seen her, or know of her whereabouts, to contact them.
Anyone with information should contact Norfolk Police on 101.
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