The father of missing Belgian backpacker Theo Hayez has broken down in tears as he made an emotional plea for help to find his son, who went missing in northern NSW more than two weeks ago.
Police admit they are "baffled" by the 18-year-old's disappearance, with no clear leads or information on his whereabouts.
The young traveller was last seen leaving the Cheeky Monkey's bar in Byron Bay about 11pm on May 31.
He was caught on CCTV footage earlier that night about 7.45pm buying alcohol in a bottleshop.
But they are the only two confirmed sightings of Mr Hayez, who was preparing to return home after eight months travelling around Australia.
He was reported missing on June 6 when he failed to return to his hostel and couldn't be contacted.
His father Laurent Hayez arrived in the country late last week and spent the weekend helping with the search, which on Monday was focused on the area around the Byron Bay lighthouse.
"I promised Theo's little brother that I would bring his brother home. Please, help me keep my promise to him," Mr Hayez told reporters through tears at Tweed Heads Police Station on Monday.
"If you have any information and if you do not want to deal with the cops, or if you are afraid to come forward, please make an anonymous call to Crime Stoppers."
Mr Hayez senior said it's believed Theo used encrypted service Whatsapp the night he disappeared and urged for help in obtaining access to the messages.
"We understand the politics about confidentiality and respect that - however, this is a question of providing assistance to a person in grave danger," he said.
"It is vital that investigators get access to Theo's WhatsApp account without delay. Every minute counts."
Superintendent David Roptell said police are inquiring with Whatsapp and its owners Facebook about accessing the messages.
While homicide detectives are helping the investigation, as well as Belgian authorities, Supt Roptell said he was still hopeful that Theo was alive.
"We're just not clear at this point," he said.
"It appears to be out of character. He was intending to go home. It's baffling as to what's occurred, but we're not ruling anything out."
Laurent Hayez thanked police, volunteers and the community for their help in looking for his son, as well as those who raised money to support the search.
He said any funds not used to find Theo will be donated to charities in Australia and Belgium dedicated to finding missing people.
Australian Associated Press