Belgian special operations forces, clad in balaclavas and with bomb disposal robots at the ready, cordoned off two streets as they raided a property in Molenbeek, a suburb of the Belgian capital, on Monday morning, according to a CNN team at the scene.
Jean-Pascal Thoreau, a spokesman for the Belgian federal prosecutor, later told CNN that no one was arrested in the raid.
Earlier, Belgian state broadcaster RTBF, citing the country's Federal Justice Department, had reported that police had made one arrest during the raid, but had not apprehended Salah Abdeslam, the French citizen at the center of a manhunt for his suspected involvement in the terror attacks.
Two of those who attacked Paris on Friday have been identified as French citizens who lived in the Brussels suburb, Thoreau told CNN on Sunday, while two cars involved in the Paris shootings had Belgian license plates, according to his office.
Seven people were arrested earlier in raids in Molenbeek after the Paris attacks, but five of them have been released, Thoreau told CNN on Monday.
Among those released was Mohammed Abdeslam, brother of the wanted man. Thoreau told CNN that the released Abdeslam brother did not know his brother's whereabouts.
Leading exporter of jihadists
The developments have brought renewed focus on the threat posed by jihadist networks in Belgium, a country that, according to one analysis, has exported more jihadists to the conflicts in Syria
per capita than any other Western European nation.
According to figures
released by the International Center for the Study of Radicalization and Political Violence
in January, an estimated 440 Belgians had taken up arms for Sunni extremist groups in the Middle East, a per-capita figure about double that of France, and four times that of the UK.
Molenbeek has a large, predominantly Muslim population of first-, second- and third-generation immigrants from North Africa that has gained an unwelcome reputation as a hotbed of jihadism.
Belgium's minister of justice, Koen Geens, told CNN's Ivan Watson on Monday that his country had "a foreign fighters problem," and he cited Molenbeek as an example of an area where more needed to be done to combat the threat.
In January, police raided a suspected ISIS terror cell in Verviers
in eastern Belgium, killing two men who were alleged to be on the brink of a major Paris-style attack.
The cell members, including the man alleged to be orchestrating the plot from abroad, Belgian-Moroccan Abelhamid Abaaoud, all hailed from the Molenbeek area
and were suspected to be ISIS
veterans who had returned from fighting in Syria, according to a counterterrorism official.
Police found automatic weapons, police uniforms and chemicals to make TATP, the powerful explosive that the Paris attackers also used Friday.
Two houses in the suburb were also raided after Ayoub El Khazzani, a Moroccan national, opened fire with a Kalashnikov rifle on a high-speed train from Paris to Amsterdam in August
. The prosecutor's office said he had spent time in Molenbeek before the attack.
The neighborhood's links to extremist Islam extend back decades. Bassam Ayachi, a French citizen and Salafist cleric, founded the Centre Islamique Belge (CIB) in Molenbeek
in the early 1990s -- an organization that Belgian authorities say espoused hardline, pro-al Qaeda views and recruited jihadist fighters.
The Belgian capital was also the site of atrocities in May 2014 that left four people dead at Belgium's Jewish Museum
. Mehdi Nemmouche, a radicalized French citizen who had spent a year in Syria, has been extradited to Belgium, where he awaits trial.
And an arms dealer from the city was arrested for allegedly providing arms to Amedy Coulibaly, the ISIS sympathizer who attacked a Paris kosher supermarket in January
Molenbeek Mayor Francoise Schepmans told CNN after January's Verviers raids that the suburb was aware of the problems it faced with a cocktail of high unemployment among youths, disaffected young Muslims and jihadist propaganda.
In February, a Belgian court convicted the leader of the Islamist group Sharia4Belgium
and several followers on terror charges of sending jihadist fighters to Syria. The offenses were committed in Brussels, Antwerp, Syria and Turkey.
"There are several people who left here to fight in Syria. And some who came back. That's the danger," Schepmans said.
Abaaoud, who authorities suspect orchestrated the Verviers plot from Greece, is believed to have joined ISIS in Syria in early 2014, Guy Van Vlierden, editor of a blog on Belgian foreign fighters, told CNN this year. At some point, his 13-year-old brother joined him there, becoming the youngest Belgian jihadist in Syria.
After the Verviers plot was foiled, Abaaoud evaded European authorities' efforts to apprehend him. He later was featured in an ISIS propaganda magazine, claiming to have returned to Syria.
Geens, the Belgian justice minister, told CNN on Monday that the jurisdictional divisions in the Brussels police force could hamper police efforts against the jihadist threat. Brussels has 19 municipal mayors in charge of six police zones with their own local police forces.
"The fact that Brussels is politically and -- as to its police forces -- a little bit more divided than one would expect from such a big city creates additional problems as to surveillance," he told CNN's Watson.
"The main thing is the local and federal police have to work together continuously. Simple and normal criminality which has nothing to do with terrorism -- but like false papers, false passports, weapon trade -- are flourishing in certain suburbs of Brussels like in Molenbeek, and we absolutely have to counter these things with the help of local services."
'Trying to talent spot' Western jihadists
In an interview with CNN terrorism analyst Paul Cruickshank
in August, Alain Grignard, a senior member of the counterterror unit in the Brussels federal police and a lecturer on political Islam
at the University of Liege, said the perpetrators of the Verviers plot fit a typical profile of Belgian jihadists: "men in their early 20s mostly from the Molenbeek district of Brussels moving in circles with a track record of delinquency and petty crime."
"They were radicalized very quickly, and when they came back from Syria they had no fear of death," Grignard said in the interview
, published in the Combating Terrorism Center
's publication, the CTC Sentinel. Cruickshank is also editor-in-chief of the CTC Sentinel.
"These guys had maybe more experience in gun battles than our own commandos."
Like many European jihadists, they were an outgrowth of the "inner-city gang phenomenon," he said, who had already revolted against Western society through petty crime and delinquency before having their antisocial approach "legitimized" by a radical strain of Islam.
"These youngsters are getting quickly and completely sucked in. The next thing they know they're in Syria and in a real video game," he said.
He told Cruickshank that the terror threat in Belgium, fueled by the trail of young jihadists to fight in Syria and Iraq, had "never been higher in all the years I've been working on counterterrorism."
"To give you an idea of the scale of the challenge, in the past two years we've charged more people with terrorism offenses than in the 30 years before that," he said. "It's impossible to do surveillance on everybody."
Since 2012, he said, al Qaeda had been "trying to talent spot" Western jihadists on the battlefields of Syria for use in potential operations against the West, while ISIS had appeared more focused on state building. But since the start of the U.S.-led air campaign targeting ISIS, the concern had grown that ISIS would also focus on directly targeting Western countries.
"And the worry is that competition between al Qaeda and the Islamic State will see both groups try to outdo each other with attacks in the West," he said.