Gardaí said today that they are treating the death of James Sheehan as a tragic accident.
A postmortem carried out on the body of the remains of the teenager found he died of natural causes.
The 18-year-old's body was recovered from the Avoca river in Co Wicklow yesterday.
James had been missing since early Sunday morning after a night out in a club with friends.
A major search of the Arklow area involving gardaí and more than a hundred local volunteers was launched amid fears the teenager had been abducted.
Local Councillor Pat Fitzgerald said that the support from the local community has been overwhelming.
"I know that they will get support in the coming days and the coming months and the coming years - because the town has great people, and certainly I was overwhelmed by the support that was shown to the family over the last few days," he said.
"On a personal level as a public representative I'd like to thank everyone who went out, who gave information, who supported them."