Bream Bay relieving Sergeant John Clayton said the forestry workers came across some bones and personal items.
Some cards including a bank card were found which helped police quickly identify the man as Mr Mariu, who was 42 when he was reported missing in September 1994.
His family were with police as they searched a steep slope about 50 metres below where the remains were discovered.
Mr Clayton said while it was a sad day for those who knew Mr Mariu, it also meant they finally had some answers.
"Obviously it was good news and bad news for them but finding the remains has confirmed what they thought," Mr Clayton said.
"It was an important day for the family."
There were no suspicious circumstances surrounding his disappearance or death.
Following mortuary procedures, the case would be handed over to the coroner, he said.
In November 2011 a coroner's hearing was held in Whangarei about Mr Mariu's disappearance.
At that time Northland Coroner Brandt Shortland formally pronounced him dead and praised the dozen relatives who attended the final official analysis of what happened to him after he disappeared.
The last confirmed sighting of him alive was on September 1, 1994, when he was given a lift from Ahipara to Whangarei.
The next day there was an unconfirmed sighting of him in Auckland.
At the end of the hearing the coroner declared Mr Mariu formally dead and said every attempt had been made to establish whether he was alive.
