An 18-year-old backpacker from Belgium walked out of his hostel in an Australian coastal town in New South Wales and disappeared. Almost two weeks later, his father made an emotional appeal to WhatsApp, saying his son’s encrypted messages could provide a crucial clue into his whereabouts.

Theo Hayez, who spent the past eight months traveling around Australia, was reported missing on June 6 when he did not return to his hostel, leaving his passport and personal belongings behind, according to a New South Wales police statement released Monday. Hayez had been preparing to return home to Belgium.

Last week, his father, Laurent Hayez, traveled to Australia to assist in the search for his son. In a news conference Monday at the Tweed Heads police station, Laurent Hayez made a public appeal for information and pleaded with the Facebook-owned company to release the details of his son’s WhatsApp messages. “We know … that Theo used WhatsApp the night he disappeared,” he said. “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.”

Earlier Monday, police released an image from closed-circuit TV that showed Theo Hayez at a convenience store on May 31, according to the police statement. The footage was released to provide details on the clothing he was wearing when he went missing and to hopefully jog someone’s memory, according to the police district commander, Superintendent Dave Roptell.

“Over the past week, the public have been actively involved in the search for Theo. Our detectives are continuing to go through all available information provided to us,” Roptell said. “We want to provide answers to his family both here in Australia and back at home in Belgium.”

WhatsApp said in a statement it was working with police in “accordance with applicable law and our terms of service.” WhatsApp does not have access to its end-to-end encrypted messages, according to the company’s security page. But messaging platforms such as WhatsApp do have access to certain information collected from its users, such as their names, the time they were last logged in and Internet-protocol addresses.

“WhatsApp cares deeply about the safety of our users and our hearts go out to Theo Hayez and his family,” the statement said.

In the United States, police are increasingly turning to tech companies to assist them in solving crimes. From January to June 2017, Facebook received 32,716 requests for information from law enforcement agencies, according to a 2018 Harvard Law Review article. The requests included 19,393 search warrants and 7,732 subpoenas over 52,280 user accounts. Among three big tech companies — Facebook, Google and Twitter — at least some information was provided for about 80 percent of law enforcement requests, according to the article.

A 2018 report by the Center for Strategic and International Studies, a Washington-based think tank, called for a national digital-evidence office that would establish national policies and training programs for digital evidence collection.

While the United States does not have federal legislation addressing the collection of digital evidence, Britain passed the Investigatory Powers Act in 2016, which provided a legal framework for international technology companies such as Google and Facebook to unscramble encrypted messages to assist police investigations. Portions of the act have been contested in the British Supreme Court.

Australia is considering similar legislation but has not passed a law requiring tech companies to cooperate with police.

“When I left Belgium, I promised Theo’s little brother, Lucas, I would bring his brother home,” Laurent Hayez said at the news conference. “Please help me keep my promise to him.”

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