When a young Belgian woman of Moroccan descent went undercover for two months in the heavily Muslim district of Molenbeek, the virulent strain of violent extremism she found should have been a wake-up call for Belgium.

Hind Fraihi, a Muslim and journalist who posed as a sociology graduate student, found that she could easily buy extremist literature urging people to take up arms to fight nonbelievers. She met young men being lured from lives of petty crime to violent jihad by local imams. And she interviewed a sheik who sent young men to a military training camp in southern Belgium’s scenic Ardennes and who was recruiting people to fight in Afghanistan and Chechnya.

Fraihi did all that 10 years ago and wrote about it in a five-part series called “Undercover in Little Morocco,” which appeared first in a Flemish newspaper and later was published as a book. It garnered a lot of notice, but little came of it in terms of policy changes.

Now, she says, because Belgian authorities have not done enough to fight extremism, “there is a whole generation waiting to participate in these actions” — such as those carried out in Paris last week. Three of the young men she interviewed then are now in Syria, as is the sheik, Bassam Ayashi, who was once linked to al-Qaeda. Ayashi, 69, is said to be leading part of the more moderate Islamic Front group fighting the Islamic State and the Syrian government of President Bashar al-Assad; his son and stepson have been killed in battle against Assad forces, and Ayashi was recently injured in a bomb attack on his car.

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They are just a few of the roughly 100 people who have left Brussels to fight in Syria. And now police and intelligence officials are wondering how many more extremists, such as those who carried out last week’s attacks in Paris, might be living openly and mixing easily in an only moderately religious, middle-class neighborhood near the heart of Brussels.

Fraihi says these are questions she tried to answer a decade ago because she felt that the radical extremists she heard about were clashing with the kind of Islam she had learned growing up with her parents, who immigrated more than 50 years ago. So she rented an apartment with a divorced woman from Morocco who had been brought over as what was known as “an import bride” to wed someone here. And Fraihi went about searching for answers.

The books preaching jihad that she bought from open book vendors were printed in Amsterdam, but the material had been written in Saudi Arabia. The books advised readers to take revenge on nonbelievers, whether Muslim or non-Muslim. They said that parliament had no authority and that only Allah’s law is sovereign, Fraihi said. And some advised readers to learn how to communicate in symbols and secret code and offered tips on how to do that.

The three youths who later went to Syria she found hanging around street corners. They had quit school and told her they passed much of their time sleeping. Or they would hang around at the metro exits and snatch people’s bags. They called it jihad because they would pick out Westerners. Fraihi told them that sounded like racism. They called it gangster Islam.

They were ripe for picking by international recruiters. “These young people don’t have a job or a future, so they are very easy to indoctrinate if you give them a big story,” she said, “a big collective story, a story of our society, a dream, an aspiration, an idealism.”

She said that in modern Western society there is “so much individualism,” and it can be hard for some people. “They are seeking something to connect with because there is a lack of connection.”

A copy of Hind Fraihi's book ‘Undercover in Little Morocco.’ (Steven Mufson / The Washington Post) (Steven Mufson/TWP)

Back then, Ayashi told Fraihi that people here live “like rats” and that jihad could give them a sense of purpose.

At the time, Ayashi ran an organization called the Belgian Islamic Center for teaching young Muslims. He also performed marriages without going through the requirements of Belgian law. Earlier, after France banned schoolchildren from wearing veils, he had written an open letter to then-French President Nicolas Sarkozy titled, “When Death Becomes Beautiful.”

Ayashi denied being an extremist, telling Fraihi that “a Muslim extremist is someone who thinks that a Muslim woman shouldn’t wear a veil and that an Islamic state is possible without Islamic laws.”

He had lived for a time in France. He had been charged in criminal cases with fraud and incitement, but eventually he returned to Molenbeek.

“Some people disappear from the radar and then come back as little ghosts,” Fraihi said, “or big ghosts.”

Ayashi was selling “something epic, something romantic that will give your life a mission. And if all day long there is nothing to do, you failed at school, you don’t have a job,” Fraihi said, “it is very easy for figures like this sheik to approach these young men.”

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The bombs exploded, and France’s president called it ‘war’. It was 1986.