CANBERRA, Australia (AP) — An encrypted phone message sent by a missing Belgian tourist could hold a clue to the 18-year-old's disappearance from an Australian coastal town, his father said on Monday.

Theo Hayez was last seen leaving a Byron Bay nightclub late on May 31. Police say they are baffled by his disappearance.

His father Laurent Hayez flew from Belgium to Australia last week to take part in the search, which now involves homicide detectives.

Hayez on Monday made a public appeal for help to access his son's encrypted WhatsApp account.

"We know ... that Theo used WhatsApp the night he disappeared. We understand the politics about confidentiality and respect that," Hayez said.

"However, this is a question of providing assistance to a person in grave danger. It is vital that investigators get access to Theo's WhatsApp account without delay. Every minute counts," he added.

Police Superintendent Dave Roptell said WhatsApp's owner Facebook was being asked for access to the missing man's account. Facebook did not immediately respond on Monday to a request for comment.

Australia is considering introducing laws modeled on Britain's Investigatory Powers Act that would force global technology companies such as Facebook and Google to help police by unscrambling encrypted messages sent by extremists and other criminals.

The search for the missing man in one of Australia's premier tourist destinations is continuing on land, sea and in the air.

Theo Hayez had been preparing to return Belgium after eight months of traveling around Australia.

He was reported missing on June 6 when he failed to return to his hostel and could not be contacted.

His last confirmed sightings were when he was captured on CCTV buying alcohol from a liquor store before he went to the Cheeky Monkey's nightclub.