A Toronto man is named on an Interpol list of individuals suspected to belong to an ISIS suicide brigade, according to a Canadian expert on radicalization and foreign fighters.

Tabirul Hasib first disappeared five years ago when he booked a flight to the Middle East along with three other Toronto men: Malik Abdul (better known as Abdul Malik) and two others — Nur and Adib — whose last names are not known.

What followed was a desperate attempt by the men's parents to keep them from falling into the hands of the Islamic State in Iraq and Syria (ISIS), beginning with missing person's reports to Toronto police. From there, officers with the RCMP's Integrated National Security Enforcement team became involved, asking tough questions of their families.

When Abdul Malik's father learned the young men were headed to Syria, he and Nur's father got on a plane and managed to convince the four to come home, where he says they were repeatedly questioned by CSIS agents and RCMP officers.

In July 2014, three of the men disappeared again.

Recruited by Timmins-born ISIS fighter

Now, five years later, Hasib's name has surfaced on a list of people who could launch attacks in the West, says researcher Amarnath Amarasingam, a fellow at the George Washington University's Program on Extremism.

CBC News first reported on Hasib in March 2015 when it was determined that he was among five people to have been recruited by Timmins, Ont.-born foreign fighter Andre Poulin, who died while fighting in Syria in 2013 at age 24. The first of the five to be recruited was a man named Mohammed Ali of Mississauga, Ont., who went by Abu Turaab, who left Canada in April 2014.

Amarnath Amarasingam is a fellow at the George Washington University's Program on Extremism. (CBC )

At the time, Hasib's mother told CBC News she was devastated at her son's disappearance; she said the last time she'd spoken to him was November 2014.

"I asked him where he was and he wouldn't answer," she recalled in 2015. "And then I was overtaken by grief and couldn't speak to him."

The list on which Hasib's name appears — along with his nom du guerre Abu Bakr al-Bangladeshi — was first reported on last month in The Guardian. The British newspaper said it was based on data collected by U.S. intelligence and circulated by Interpol on May 27.

Stark contrast to a former life

According to The Guardian, the list says those named "may have been trained to build and position improvised explosive devices in order to cause serious deaths and injuries. It is believed that they can travel internationally, to participate in terrorist activities."

CBC News has not obtained an original copy of the list, but The Guardian reports that it contains the suspects' names, their recruitment dates, their last likely addresses, their mothers' names and any available photographs.

Hasib's appearance on it comes as a surprise to Amarasingam.

On ISIS entrance forms, Hasib is listed as someone who wanted to be a fighter, he notes — not someone looking to be a suicide bomber.

The former Monarch Park Collegiate student and apparent graduate was active in his school's athletic program, participating in long-distance running competitions before enrolling in Centennial College. It's a stark contrast to his portrayal on the list as an aspiring bomber with a suicide brigade.

There is also the possibility that Hasib's identity could have been used by someone else.

"When a lot of these travellers arrive in Syria and join the Islamic State, one of the first things they do is confiscate documents. We don't know if they get them back or if they're passed on or used for another purpose," assistant professor at Carleton University Stephanie Carvin points out.

Whether Hasib, who would now be 25, is still alive is not yet known. At least two of his three friends are believed to be dead.

In 2015, Abdul Malik's father told CBC News he received a phone call from Hasib saying his son had been killed along with one of the other two men around the time of a major ISIS offensive in the Syrian border town of Kobani.

"This likely means that he joined this so-called suicide brigade later on, possibly after his friends were killed," Amarasingam told CBC News. Meanwhile, Abdul Malik's brother Abdul Kadir, who court documents say also wanted to join the fight in Syria, has been on a peace bond since last year.

For Amarasingam, the fact that the men were allegedly helped into Syria by Mississauga's Abu Turaab underscores how friendships formed at home became critical in their entry into extremist groups abroad.

"These trust networks established in Canada on the streets of Scarborough are playing out in war zones in the Middle East," Amarasingam said.

Rethinking the 'returnee assumption'

Hasib's appearance on the list also means the focus on Canadians returning home after travelling abroad to fight with ISIS is perhaps too narrow, Amarasingam says.

According to a 2016 report by Public Safety Canada, 180 people with Canadian connections have travelled abroad to join ISIS and other terror groups, and at least 60 of them have returned.

"I think we are operating under the 'returnee' assumption, which says that Canadians will go back to Canada, French will go back to France and so on. It doesn't have to be that way," Amarasingam said. "Their goal is to attack the West."

The majority of those on the Interpol list are of Iraqi nationality, says Amarasingam, a finding he calls worrying, as they may not be on the radar of most Western law enforcement.

However, there are a handful of names from Western countries, says Amarasingam, including those from Germany, Switzerland, France and the Netherlands.

"There seems to be a fear that the majority of those on the list — Iraqis — may make use of the refugee flows into Europe," said Amarasingam.

"It pains me to say that because I know what some politicians will do with that kind of statement."

The Canadian government would not confirm if it is aware of the Interpol list, saying it does not comment on national security operations.

A statement from Public Safety Minister Ralph Goodale's press secretary Scott Bardsley said only that "Canada monitors all potential threats and has robust measures in place to address them."