Locked WhatsApp Messages Could Hold Key To Finding Théo

Belgian teen Théo Hayez has been missing for close to three weeks with NSW police admitting they are "baffled" by the case and are not ruling out any lines of inquiry.

Now, Theo's desperate family are hoping his locked WhatsApp messages may hold clues as to what happened to him.

Théo's cousin, Lisa Hayez, has been leading the search for the missing 18-year-old, since he disappeared after leaving the Cheeky Monkey bar in Byron Bay at about 11pm on May 31.

Lisa, who told 10 daily his family was desperately searching for answers both in Australia and from his home in Belgium, believes his WhatsApp messages may hold vital information about his whereabouts on the night he disappeared.

Théo Hayez has been missing since May 31. PHOTO: Lisa Hayez

"We really need to access to his Whatsapp because there is a big possibility that he might had a conversation with someone that night that could change everything," Lisa said in a post on Facebook on Sunday.

She has been asking hundreds in the local community and on social media to share the posts and others linking to her missing cousin, in the hopes WhatsApp will see the message and get the information to police faster.

On Monday, a spokesperson for WhatsApp said the service was assisting law enforcement in accordance with applicable law and its terms of service.

"WhatsApp cares deeply about the safety of our users and our hearts go out to Theo Hayez and his family," the spokesperson said in a statement.

10 daily understands WhatsApp does not have access to users' encrypted conversations, but can provide information including a user's name and photo, when the service was first used and last seen, as well as IP address and numbers blocking or blocked by the user.

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Earlier Lisa told 10 daily she had last seen her cousin just a few days before he disappeared after the two caught up for a weekend.

In a touching message last week, Lisa shared a photo with Théo in which she wrote: "come on, come back little cat".

Théo has been described by his family as "always happy and smiling".

Lisa and Theo. PHOTO: Supplied.

The 18-year-old had been backpacking around Australia since November and was due to return home to Belgium last week.

Police have located his belongings, including his passport, in his hostel room in Byron Bay and they say the teenager has not used his phone or made any financial transactions since he disappeared.

On Monday police said they could confirm two sightings of Théo on the night he disappeared. The first at 7:45pm at a bottleshop and the second leaving the Cheeky Monkey's nightclub after 11pm.

Investigators are now calling for anyone who may have any information or CCTV or dashcam footage from the night of his disappearance to come forward.

"I urge you to look and hopefully if people were in the area at that time that they may have recognised or have some information that is leading to the disappearance of Théo Hayez because I'll say it again - we are baffled, we have baffled because that is all we have.

Police have also confirmed that homicide detectives have also joined in the investigation, but stressed it was just one of many lines of inquiry.

On the weekend, Théo's father Laurent arrived from Belgium and joined the desperate search for his son.

In a brief statement to media on Monday, Laurent broke down as he thanked emergency services and the community for the efforts in trying to find his son.

"Thank you to everyone who gave to the crowd-funding set-up by our friends which has allowed me to come to Australia," he said.

"As soon as we have realised the success of the crowd-funding, Théo's mother and I agreed that any funds that remains when Theo is found will be split between one Belgian and one Australian charity dedicated to finding missing people."

I promise Theo's little brother, Lucas, that I would bring his brother home. Please, help me keep my promise to him.

Last week the search for missing Théo was expanded to the water with police using a specialist drone in the area, while surf lifesavers took to the waters off Byron Bay.

It comes after extensive land searches by authorities and community members failed to find any trace of the missing teenager.

Théo, who was last seen wearing a black hooded jumper, beige pants and black shoes, is described as being approximately 180-190 centimetres tall, with a thin build and blond hair.

Police are continuing to ask for any information or sightings of Théo that would "greatly assist" investigations.

Investigators were particularly looking for any CCTV or dashcam footage from the surrounding area from 11pm on Friday 31 May.

Anyone with information is being urged to contact police or Crime Stoppers on 1800 333 000.

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