The man, who is the brother of a well-known Irish sports star, relocated to Marbella in southern Spain several years ago amid the Hutch-Kinahan feud due to concerns for his safety.
An Garda Síochána has been working closely with Spanish authorities in efforts to locate him.
Concerns for the Dubliner's welfare intensified earlier this week following a fatal shooting in Barcelona, with speculation emerging that he could have been the victim.
The victim was shot in the head on Carrer de Balmes in Barcelona on Wednesday morning.
However, Gardaí believe this is unlikely to be connected to the missing man. Barcelona is more than 1,000 kilometres from Marbella, where he was last reported missing, and investigators do not believe the deceased was Irish.
A spokesperson for the Catalan police said that, due to the ongoing nature of the investigation, no further information regarding the murder will be released at this time.
Spanish police have confirmed that they will continue to work alongside An Garda Síochána in the search for the missing man.
