Update - August 4, 1.30pm: Sean Costello has been found safe and well.
Earlier: Gardaí in Dublin are seeking the public's assistance in tracing the whereabouts of a missing 15-year-old boy from Ballymun.
Sean Costello was last seen just after midnight on Sunday, July 31 on Balcurris Road in Ballymun.
He is described as 5ft 9 in height, of slim build with short, tight hair.
He was last seen wearing a navy Hugo Boss polo shirt, light blue jeans and navy Nike runners.
Gardaí are concerned for his welfare and are appealing to anyone with information to come forward.