Belgian authorities have released more details about the suspects linked to the deadly terror attacks in Brussels. (Claritza Jimenez/The Washington Post)

Belgian authorities have released more details about the suspects linked to the deadly terror attacks in Brussels. (Claritza Jimenez/The Washington Post)

After a series of embarrassing failures, Belgian authorities announced apparent progress Saturday in their efforts to unravel a web of interconnected terrorist plots and said they may have found the most-wanted remaining suspect in Tuesday’s devastating suicide bomb ­attacks.

The arrest, if confirmed, could help ease some of the jitters in a city that remained palpably on edge Saturday as organizers were forced to call off a planned solidarity rally because authorities acknowledged they could not secure the site.

Since the bombings, which killed at least 31 people and ripped apart an airport and a subway car, police have been hunting nationwide for “the man in white” — a figure dressed in a white jacket and black hat who appeared on surveillance footage alongside two others who would blow themselves up minutes later.

Authorities said Saturday that they are investigating the possibility that the man, who is thought to have deposited a piece of explosives-laden luggage in the departures hall and then fled, may already be in custody.

The arrested man, identified by a European official as Fayçal Cheffou, appeared before a judge after he was detained Thursday night while sitting in a car in front of the Belgian prosecutor’s office. He was charged with “participation in the activities of a terrorist group, terrorist murders and attempted terrorist murders.”

A spokesman for the federal prosecutor’s office, Eric Van der Sypt, confirmed that the man identified by his office only as “Fayçal C.” was being investigated as the possible third airport attacker. But he said the link “cannot be confirmed yet.”

“We have to be 100 percent sure,” he said. “These are very heavy charges.”

Belgium’s Le Soir newspaper reported that Cheffou was the man in the video, citing an unidentified source who said that a taxi driver who took the attackers to the airport the morning of the bombings positively identified him.

Belgian media reported that Cheffou has in the past identified himself as “an independent journalist” and has a history of advocacy on behalf of radical Islamist causes. He was reportedly once arrested for trying to recruit refugees in a public park and later received an order to stay away.

The website of Flanders News posted a video that it said featured Cheffou reporting in front of an asylum center, where he tells viewers that mealtimes for detainees were not altered to account for Ramadan, when Muslims must fast during daylight hours. “This goes against human rights,” he says in the video.

Unlike the other two airport bombers, the third man’s bag never detonated. The first two wore black gloves on their left hands that authorities believe concealed the detonators. The third man did not wear gloves.

[Security forces missed chances before the Brussels attacks]

The prosecutor’s announcement comes just a day after investigators revealed that they may have missed a crucial opportunity to disrupt plans for the Tuesday killings. In the days before the attacks, investigators were questioning Salah Abdeslam, the last living direct participant in November’s Paris terrorist attacks. He had been arrested in Brussels only four days before the Belgium attackers struck.

But the investigators focused their inquiries on the Paris attacks and on the procedures for extradition rather than press ­Abdeslam on plans for future strikes.

French newspaper Le Monde published in Saturday’s edition what it claimed were excerpts from a transcript of prosecutors’ questioning of Abdeslam. At one point, they show him photos of the two brothers who days later would attack the Brussels airport and subway, Ibrahim and Khalid el-Bakraoui.

“I did not know them,” Abdeslam replies, according to Le Monde. The prosecutors move on, even though they had already uncovered Abdeslam’s fingerprints in an apartment rented by Khalid el-Bakraoui.

In addition to Cheffou, two others were also charged Saturday with terrorism-related offenses, though they were not directly linked to Tuesday’s attack.

Prosecutors said they charged a man identified as “Rabah N.” with “participating in the activities of a terrorist group” in connection with a Thursday raid in the Paris suburb of Argenteuil that French leaders say foiled an imminent attack on France.

Also connected to that plot is a man who was detained in a raid in Brussels on Friday, Abderrahman Ameroud, several Belgian media outlets reported, citing unnamed police sources. Ameroud, an Algerian, was sentenced in 2005 in France to seven years in prison for recruiting jihadists to fight in Afghanistan as part of a case tied to the 2001 assassination of anti-Taliban leader Ahmed Shah Massoud.

Another man, identified as “Aboubakar A.,” was arrested and charged Saturday with a terrorism-related offense. But prosecutors did not specify whether he was involved with one of the known plots.

[Pentagon: Senior Islamic State commander is killed in Syria]

The flurry of arrests and charges came as airport authorities said Saturday that investigators had finished work at the scene and that workers had begun the process of repairing the badly damaged facility. The airport will be at least partially reopened — but not before Tuesday, exactly a week after the attackers struck.

Much of normal life in Brussels has resumed, with the metro system reopening a day after the attacks and the streets once again clogged with pedestrians and traffic. But there are also signs of continuing fears.

Belgian Interior Minister Jan Jambon on Saturday appealed to residents not to attend a solidarity rally that had been planned for Sunday, saying that police are stretched too thin by their investigation to properly secure the site of the march.

The march had been planned for the plaza in front of the city’s historic stock exchange building, the scene of a continuous vigil since Tuesday’s attacks. On Saturday, hundreds of people were gathered there to sing, write chalk messages and reflect as camouflage-clad soldiers cradling assault rifles paced nearby.

“We understand fully the emotions,” Jambon said. “We understand that everyone wants to express these feelings.”

But Brussels Mayor Yvan Mayeur said that given the number of investigations underway, the rally should be postponed — and organizers agreed.

[Families still in desperate wait for news after attacks]

“Let us allow the security services to do their work, and the march, which we, too, want to take part in, be delayed for several weeks,” Mayeur said at a news conference with Jambon at the national crisis center.

The announcement represented a striking admission by authorities that they are overwhelmed by the difficulty of piecing together information about homegrown jihadist networks that are far more extensive than previously thought.

A Mariah Carey concert scheduled for Sunday was canceled late Friday, with the singer announcing on Twitter that she had been “advised to cancel my show for the safety of my fans, my band, crew and everyone.”

Belgium’s federal crisis center increased its estimate of the number of wounded to 340 on Saturday, and it said 27 of the 31 thought to be dead had been identified. Nearly half of the victims were foreign, and they came from eight countries, the center said.

Stephanie and Justin Shults, an American couple living in Brussels, were declared dead on Saturday, according to members of Justin Shults’s family.

A U.S. official, who spoke on the condition of anonymity to discuss the status of Americans overseas, said that about a dozen U.S. citizens were wounded in the attacks. At least two Americans were killed.

CORRECTION: An earlier version of this article reported that at least four Americans were believed to be dead in the attacks. At least two Americans have been confirmed dead.

Missy Ryan, Annabell Van den Berghe and Souad Mekhennet in Brussels contributed to this report.

Read more:

In Syria and Iraq, the Islamic State is in retreat on multiple fronts

Anti-terrorism crackdowns may have spurred attackers, Belgian prosecutor says

The many missing pieces in the Brussels attacks investigation

New ISIS recruits have deep criminal roots