A hand grenade dating back to the Irish War of Independence was discovered by council staff who were clearing out a house in Sallynoggin, South Dublin on Wednesday, February 2.
Army bomb disposal experts responded to the property and removed the grenade to a nearby park and destroyed it after being alerted by the council staff.
Council staff re-entered the property once it was declared safe but found decomposed human remains shortly afterward.
They once again notified gardaí and the remains were examined in situ by a pathologist before they were removed for a post-mortem.
Gardaí do not suspect foul play and believe that the man may have died 12 months ago during lockdown.
DNA testing and dental records are being used to confirm the man's identity.
The man has been described as a hoarder who did not mix with others in the community.
Gardaí are speaking to locals to determine when they last saw or heard from the man.
The South Dublin County Council had made efforts to contact the man and moved to clear the property as they believed it had been abandoned.
Workers found the house in a state of disrepair.
Gardaí in Dún Laoghaire are investigating "all the circumstances" in relation to the discovery of the man's body in a house on Sallynoggin Road Lower, according to the Irish Times.
The investigation is thought to be at an early stage, although gardaí suspect that the man died 12 months ago, possibly more.