Fears are growing for a 15-year-old girl who went missing from her school on Monday.
Billie Dickerson was seen leaving class at Winston Churchill School in Woking, Surrey, at 2.30pm but never arrived home.
Police believe she could have travelled to London or Hull - where she has relatives – although they say there has been no confirmed sighting since Monday.
A CCTV image has been released which shows the schoolgirl walking through the subway at Woking railway station between Oriental Road and the town centre, around 5.50pm that evening.
Further CCTV shows her in the Peacocks shopping centre around 6.10pm. Billie was reportedly seen near the school again yesterday and police are carrying out enquiries to confirm this sighting.
Her worried older sister Charlotte made a plea on Facebook: "Please help me find her. She is still missing we just want to know that she is safe."
A Surrey Police spokesman said: "Officers are growing increasingly concerned for her welfare and are appealing for any members of the public who may have seen her to contact police."
She added that Billie did not live with either of her parents in Woking, but did live with a relative.
The teenager, a member of her local Sea Cadets group, is described as white, 5ft 2ins tall, slim with long brown hair.
She was wearing a blue hooded top over her school uniform, but was carrying a bag with her that may contain other clothes.
Anyone who may have seen Billie should contact Surrey Police on 101 or Crimestoppers anonymously on 0800 555 111.