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Authorities detain six people following overnight raids in Brussels

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BRUSSELS, Belgium (CNN) — Three days after the gruesome Brussels bombings that left 31 people dead, the concerns are palpable.

Can Europe keep up with terror cells and foil their plots before the next deadly attack?

Investigators already know about ISIS plots in Europe that are in various stages of preparation.

French authorities arrested a man suspected of plotting an attack that was in an “advance stage” of planning.

And with at least one — possibly two — of the Brussels bombers still on the loose, the race is on to prevent another wave of terror.

Raids, roundup in Brussels

Police launched a series of raids across Brussels overnight, detaining at least six people.

Three people in a vehicle were detained right outside the prosecutor’s office, public broadcaster RTBF reported. Two people were taken into custody in Brussels’ Jette neighborhood, and one person was detained in a different part of the Belgian capital.

On Friday morning, police conducted another raid in the Forest neighborhood of Brussels, leading to more arrests. But officials did not say how many people were detained.

The Belgian federal prosecutor’s office didn’t say who was arrested, why they were apprehended or whether they will face charges. It said officials will determine Friday whether some of those detained will remain in custody.

The tactic of detaining people first and asking questions later will likely become increasingly common, CNN national security analyst Juliette Kayyem said.

“There will be lots more of them,” she said. “They are going to be what’s called overbroad. They are going to just try to find people or evidence that may stop the next terrorism attack, and they will figure out who they have under custody.”

At this point, any clue, any lead, any witness could be critical in the race to stop the next terrorist attack on European soil.

Belgian official: ‘We missed the chance’

Of the five suspects from the Brussels Airport and subway attacks, officials have identified three: brothers Ibrahim and Khalid El Bakraoui, and suspected ISIS bomb-maker Najim Laachraoui.

All three of those suspects are dead. And all three had been alerted to Belgian officials prior to the attacks.

The European police agency Interpol issued a “red notice” for Laachraoui, saying he was wanted for involvement in association with terrorists and the unauthorized engineering of explosives.

Khalid El Bakraoui was also the subject of an Interpol red notice three months ago; he was wanted on suspicion of terrorism.

And his brother, Ibrahim El Bakraoui, traveled to Turkey last June. Turkish authorities deported him for trying to join ISIS and sent him to Holland.

Dutch authorities said they received an email from Turkish officials 26 minutes before Ibrahim El Bakraoui’s flight — but it never mentioned Turkey’s concerns.

It wasn’t Ibrahim El Bakraoui’s first run-in with authorities. In 2010, he sentenced to nine years in prison in Belgium for opening fire on police officers during a robbery, according to broadcaster RTBF and CNN affiliate RTL. Obviously, he didn’t serve all that time.

Belgian Interior Minister Jan Jambon acknowledged the missed opportunity to stop Ibrahim El Bakraoui, one of the Brussels airport bombers.

“Given the facts, it is justified that … people ask how it is possible that someone was released early and we missed the chance when he was in Turkey to detain him,” Jambon said.

On Thursday, Jambon offered to resign as interior minister. But he said Prime Minister Charles Michel refused to accept the resignation “given the situation we are in.”

‘The feeling of war’

On the streets of Brussels, commuters are trying to get back to their normal lives. But the anxiety is still high.

“We all know that we are not safe anywhere,” one woman said. “It can happen anywhere and at any moment.”

Soldiers now line the streets near the central subway station, their hands gripping guns.

“It’s a little bit kind of war — the feeling of war,” one Belgian man said.

Now, everyone who wants to board the subway gets searched.

Some say they’re glad for the extra precautions in Brussels.

“It makes me safe,” one woman said. “A lot safer.”

But it will be several more days before anyone can fly in or out of the capital. Brussels Airport said passenger flights will not resume until at least Sunday.

“Because the forensic investigation is still underway, we currently have no access to the building,” the airport’s website states. “Until we can assess the damage, it remains unclear when we can resume operations.”

Chasing unknown suspects

But the manhunt continues for at least one — possibly two — people involved in Tuesday’s attacks.

Authorities have not identified a man seen on surveillance footage wearing a beige jacket and black hat.

They believe that man, who was walking alongside Laachraoui and El Bakraoui, planted a bomb at the Brussels Airport and walked away.

That bomb didn’t go off. Authorities later detonated it in a controlled explosion.

The other identified suspect is even more mysterious.

Authorities believe an unidentified person is the second suspect involved in the subway attack, in addition to Khalid El Bakraoui, a senior Belgian security source told CNN.

Surveillance footage shows the man holding a large bag at the metro station, according to Belgian public broadcaster RTBF.

But investigators don’t know where that suspect is — or whether he’s dead or alive.

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