The girlfriend of missing backpacker Theo Hayez has spoken out, urging people to keep searching for the young man who disappeared a month ago.

Sharing a post to Facebook, the young woman has told friends and family her and Theo's loved ones need the continued support, asking them to share a missing person Facebook post from the Tweed-Byron Police.

Theo's girlfriend, Severine Marcotty, made the post earlier this month after Theo disappeared on May 31 after leaving the Cheeky Monkey bar in Byron Bay. The backpacker's mobile last sent a "ping" to a phone tower on June 1.

Last week authorities scaled back the search effort, as extensive search efforts across the Byron area have failed to produce a solid lead.

"Need your help … Please share," Ms Marcotty wrote on Facebook, sharing a screenshot of a missing person post from the Tweed-Byron Police.

Her post has been shared over 500 times and includes messages of love and support from her friends, family, and strangers.

"Every day where we are together is the most beautiful day of my life," Ms Marcotty wrote on a photo of the couple she shared in April this year.

Dog, foot and aerial searches have failed to locate Mr Hayez's clothing or phone, which volunteers felt could be key to learning his fate.

Mr Hayez's father Laurent arrived in Australia from Belgium about a fortnight ago as local volunteers intensified door-to-door efforts to find the missing traveller.

Laurent made an emotional plea for information and promised Theo's younger brother he would bring his sibling home.

Tweed-Byron Police commander, Superintendent Dave Roptell, earlier said the police were "baffled" by the young man's disappearance.

"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," he said.

NSW Police said "all lines of inquiry" were being investigated, however the involvement of homicide investigators in the case is routine, and no evidence has been found suggesting foul play.

Local police and the NSW Homicide Squad had been working with their Belgian counterparts throughout the investigation, NSW Police said.

"Belgium Police have sought authority to travel to Australia to support the ongoing investigation in an observer capacity," a spokeswoman said in a statement yesterday.

The European investigators are expected to arrive in the northern NSW town soon.

Bad weather put a halt to searches late last week, but further police operations are planned, with rain expected to break over the coming week.

Theo's mother arrived in Australia on Sunday and has met with local volunteers.

The Hayez family are being assisted by a Gofundme page set up to support them while they search for Theo.

Laurent, earlier said the family was committed to donating leftover funds to Belgian and Australian missing person charities once his son was found.

- with AAP