Police now believe that Co Donegal teenager Caolan Page may have died following a tragic accident.
The 19-year-old was found critically injured on Magazine Street in Derry city centre in the early hours of Saturday morning
Mr Page was from Carrigans, just across the border in Co Donegal.
He had sustained serious head injuries and was taken to Altnagelvin hospital in Derry where he later died.
The teenager was an A level student at St Columb's College in Derry and it is understood he had gone out with friends and became separated from them.
Initially police suspected Mr Paige may have been the victim of an assault and were appealing for eye witnesses to come forward.
A post mortem examination is to be carried out on his body this afternoon.