Belgian authorities have applied to join the search for missing backpacker Theo Hayez in Byron Bay, on NSW's north coast.
Belgian police are heading to Byron Bay to support the search by Australian authorities for missing backpacker Theo Hayez.
The 18-year-old was last seen on CCTV walking through the popular seaside NSW town after leaving the Cheeky Monkey's bar about 11pm on May 31.
The last "ping" from Theo's phone was recorded on June 1 in the area around the Cape Byron Lighthouse.
Dog, foot and aerial searches have failed to locate his clothing or phone, which volunteers feel could be key to learning his fate.
Theo's father arrived in Australia from Belgium about a fortnight ago as local volunteers intensified door-to-door efforts to find the missing traveller.
He made an emotional plea for information and promised Theo's younger brother he would bring his sibling home.
Local police and the NSW homicide squad have 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 on Thursday.
The European investigators are expected to arrive in the holiday town shortly - though no fixed timeline has been released.
NSW Police said "all lines of inquiry" are being investigated but AAP understands the homicide squad's involvement in the case is routine and no evidence has been found suggesting foul play.
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 want to stay in Australia until Theo is found.