Mountain rescue teams, police and volunteers are searching for missing 19-year-old James Corfield, from Montgomery, who was last seen at the White Horse public house, Builth Wells, at around midnight on Monday.
He is described as being 6ft 2 inches tall, of slim build, with short brown hair. He was last seen wearing a blue Abercrombie and Fitch shirt and jeans.
James was reported missing shortly before 2pm on Tuesday after failing to meet his family at the Royal Welsh Show, where he had been camping with friends.
A spokesperson for Gwent Police said: "We would like to thank the public for their offers of support and ask that local people assist the investigation by checking their gardens, sheds and other outbuildings for any signs of James. Officers are following all possible lines of enquiry and are being assisted by specialist search teams at a number of locations around Builth Wells, today."
"We are appealing to anyone who has seen James, or has any information on his whereabouts, to contact them by phoning 101."
If you are deaf, hard of hearing or speech impaired, text the non-emergency number on 07811 311 908.
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