Since this story was published, Haleema Mustafa and Ikar Mao have been released from custody without charges. Read the latest updates on this story.

The RCMP has been combing through the background of two Canadian newlyweds who disappeared while on vacation in Turkey and are suspected of trying to join ISIS, according to multiple sources.

Haleema Mustafa and Ikar Mao, both in their early 20s, have been in Turkish custody since July, according to the Turkish Embassy in Ottawa. Sources with direct knowledge of the case tell CBC News Turkish authorities are preparing to lay terror-related charges against the couple.

Sources also say they disappeared while they were travelling with family. According to those sources, Mustafa's family feared Mao had an interest in ISIS and intended to go with his wife across the border into Syria. Her family frantically contacted Turkish authorities for help when they couldn't locate her.

Mustafa's family has not responded to repeated requests for comment. Mao's family has declined comment.

It is not known whether Mao and Mustafa engaged in any extremist activities while in Turkey or in Canada or the exact details of the charges Turkey is preparing. Turkish sources say they could face anything from minor charges of sympathizing with a terrorist organization to more serious terror-related infractions.

Syrian Democratic Forces and U.S. troops patrol near the Turkish border in Hasakah, Syria, in 2018. The countries share a border of 822 kilometres and many foreign fighters looking to join ISIS have used it as a way to enter Syria. (Rodi Said/Reuters)

Security officials say the pair were not on any watch list and were not being monitored by Canadian officials.

Mao has a public profile on Couchsurfing.com, a website that helps travellers connect with people willing to let someone stay in their homes.

It shows Mao's last log-in was about three months ago. In it, Mao explained that he and his wife were looking for a place to stay in the Turkish city of Sanliurfa as they tried to learn Turkish and Arabic. He wrote that he and his wife wanted to move there soon.

Sanliurfa is not a typical tourist destination in Turkey and is less than 50 kilometres north of Turkey's 822-kilometre border with Syria.

Many foreign fighters have entered Syria through that border to join ISIS. While a coalition effort involving U.S. and Kurdish forces managed to contain ISIS in recent years, Turkey's recent incursion into northern Syria to fight the Kurds has led many imprisoned ISIS militants to escape.

Global Affairs Canada and Public Safety would not say why Mao and Mustafa are in custody or whether the couple is considered a threat to public safety.

All Global Affairs would say is that it is aware two Canadian citizens are being detained in Turkey. "Consular services are being provided and officials are in contact with the individuals' families. Consular officials in Ankara are in contact with local authorities to gather additional information," said spokesperson Barbara Harvey in an email.

Friends, family confirm RCMP investigation

Friends and family members in Canada confirmed RCMP have been in contact with them as part of an investigation into whether the couple was radicalized or had expressed any extremist views. RCMP are not commenting on the matter.

Jessica Davis, the president of Insight Threat Intelligence in Ottawa, said there could be a number of reasons why the couple is being detained and urges against making assumptions about what they were doing.

"This may turn out to have been a complete misunderstanding or some sort of domestic dispute amongst the family members that unfortunately turned into a bit of a national security issue for Canada and Turkey," she said, adding that it may be RCMP is only investigating the couple based on information Mustafa's family gave Turkey.

Mustafa and Mao were married in Mississauga in December 2018.

When she was 18, Mustafa advocated for the hijab as a fashion statement for Muslim women, in part to challenge the idea it is a restrictive piece of clothing. In a 2016 interview with CBC Radio's Metro Morning, Mustafa said, "It's a part of my look. It's part of how I portray my modesty and my religion."

Ikar Mao was charged with participating in the activity of a terrorist group and leaving Canada to participate in the activity of a terrorist group. This photo is from his public profile on Couchsurfing.com. (Ikar Mao/Couchsurfing.com)

Speaking to CBC Television News in 2016 about French police stopping a woman from wearing a burkini on a beach, Mustafa said, "You have all these countries with extremist men who are forcing women to wear hijab, and then you have these French politicians that are forcing women to uncover, so they are sort of becoming the same person. They think ISIS is their enemy, but they are slowly becoming their enemy."

Mustafa studied social services

According to her LinkedIn page, Mustafa studied social services and had moved on to a degree in human rights and equity studies at York University. She worked with kids, newcomers to Canada and adults with developmental disabilities.

Mustafa comes from a well-respected family in Markham, Ont. Her father, Shahzad Mustafa, is a successful businessman and an advocate for peace who has participated in events against Muslim extremism. He also helped create FosterLink, which helps connect Muslim foster children with Muslim families.

While immediate family did not want to speak about the case, CBC News has spoken with more than a dozen people who know Mao and Mustafa.

A friend of Haleema Mustafa told CBC News they have been worried because they have not heard from her in a while.

When she was 18, Mustafa advocated for the hijab as a fashion statement for Muslim women, in part to challenge the idea that it's a restrictive piece of clothing. (Tina Mackenzie/CBC)

Those who know Mao describe him as "friendly" and a "nice guy." Former soccer teammates said he was a talented midfielder who was religious and close to his family, which runs several businesses in southwestern Ontario.

One former car dealership co-worker described Mao as a respectful, courteous and eager employee and a very devout Muslim. The co-worker said Mao quit the job, in part, because he could not reconcile the idea of selling cars for profit with his faith. The York University Muslim Student Association's 2018 financial report lists him as a public relations officer.

On Mao's LinkedIn page, he wrote he was studying international development and expressed interest in development work in Africa, including farming. Online video shows his family taking part in development visits to Somalia, where they worked with a food security and agriculture group.

Mao and Mustafa's social media presence is limited. Mustafa's Instagram account has been taken down and her Twitter account has been suspended. Mao's Twitter account no longer exists.

Held on criminal or immigration grounds?

Leah West, who lectures on national security and intelligence issues at Carleton University in Ottawa, said, "I am really interested in knowing under what grounds they're being detained, and if they're being detained on criminal grounds or being detained on immigration grounds, because that'll really affect the role of Canadian officials."

West said that if the couple is being detained on criminal charges, there is little the Canadian government can do.

Canada doesn't have an extradition treaty with Turkey, but West said if either Mao or Mustafa is convicted of any crime, there is an agreement between the countries allowing Canadian citizens to serve their time in Canada.

She said it is likely the Canadian authorities are looking for answers.

"RCMP and potentially CSIS would be trying to understand the motivations, what's really going on, if these two did have an intent to join ISIS, and they'd be sharing information with their partners in Turkey," West said.

Long-term travel implications?

Davis said the couple's names have likely been shared with other countries, too.

"The real problem here is that once those names become public, you can't unring that bell," Davis said. "There may be long-term travel implications for these individuals, certainly some risks involved in any travel to some jurisdictions."

Speaking generally, Davis said, "There is still an interest from individuals to travel to join the Islamic State, even though it's not necessarily a state anymore."

Last year, Amnesty International raised concerns about what it called the "arbitrary, lengthy and punitive pre-trial detention and fair trial violations" it routinely observed for those facing terror charges in Turkey.

Human Rights Watch has also been critical of terrorism-related trials in Turkey, noting last year that they often "lack compelling evidence of criminal activity or acts that would reasonably be deemed terrorism."

According to the United Nations, there are 3,000 ISIS members still operating in Syria. It says despite the group's military defeat, it is still a threat to global peace and security.

In its 2018 report on the terrorism threat in Canada, Public Safety said there were approximately 190 people linked to Canada suspected of travelling abroad to take part in extremist activities.

Approximately half of those travellers are in Turkey, Syria or Iraq. Public Safety reports 60 people who are believed to have engaged in extremist activities have returned to Canada.