Investigators are appealing to anyone who was in the area at around 4.15am to come forward.
The Garda Ombudsman Fiosrú is investigating the circumstances surrounding the death of a man in Dublin city last week.
An incident involving the serious harm of a 51-year-old man on O'Connell Street in the early hours of last Friday the 15th of August was referred to Fiosrú.
The man has since died and a post mortem exam is due to be carried out.
Investigators are appealing to anyone who was in the area at around 4.15am to come forward.

Sharp Rise In M9 Collisions With Garda Call-Outs Up Year-On-Year
Councillor Seeks Clarity On How Often Nightclubs and Late Bars In Naas Are Inspected For Fire Risks
New Figures From CSO Reveal How Much International Protection Applicants Earn Compared To Average Worker In Ireland
Unpaid Eight-Month Work And Training Placement For Adults With Disabilities Branded "Extremely Unfair"
Department Of Education Defends Kildare SNA Cuts Amid Claims Of Reduced Need At Some Schools
Naas Nurses Threaten Escalation As Staffing Row Deepens
Driving Tests Face Disruption As RSA Testers To Strike Next Week
Jury Delivers Not Guilty By Reason Of Insanity Verdict In Ballyfin Demesne Strangling Case