Police have issued an appeal for information after a man from Talgarth was reported missing on Tuesday, January 3.
David Skeen, aged 51, was last seen when he left his home to go for a run at about 9am.
He was wearing an orange gilet, black running trousers, pale trainers and a blue hat.
He is described as being of slim build, 5’ 8" tall and has short fair hair.
A mobile police incident room has since been set up in Talgarth town car park.
A police statement released on Tuesday evening said: "Police are appealing for information regarding a missing 51-year-old male from the Talgarth / Velindre area.
"The male is described as very slim, 5’ 8" with short fair hair, wearing an orange gilet and long black running trousers, pale trainers and a blue beanie style hat.
"Please tel Brecon Police Station on 101 if you see this male quoting ref 139 of 03/01/2017."
Several Mountain Rescue Teams, including Longtown and Brecon, are involved in the search as well as members of Dyfed Powys Police Force.