BRUSSELS — The attacks in Brussels Tuesday were carried out by two brothers who detonated suicide bombs, Belgian officials said Wednesday, as the police continued an intense hunt for at least one other participant in the attacks. The toll from the assaults stood at 31 dead and 270 injured.
The brothers — Ibrahim el-Bakraoui, 29, and Khalid el-Bakraoui, 27 — were Belgian and had criminal records, officials said. But the pair had no known links to terrorism until authorities conducted a raid on March 15 on an apartment in the Forest district of Brussels, as part of their investigation into the Nov. 13 attacks in Paris.
Ibrahim el-Bakraoui and another man blew themselves up at the airport at 7:58 a.m., in two explosions, nine seconds apart, Frédéric Van Leeuw, the Belgian federal prosecutor, said at a news conference. At 9:11 a.m., Khalid el-Bakraoui carried out a suicide attack at the Maelbeek subway station. It was not clear whether the younger brother also participated in the airport attacks.
The search continued for a man who was recorded by a security camera alongside Ibrahim el-Bakraoui at the airport, who was believed to have fled.
After the attacks, a taxi driver approached the police and led them to a house on Rue Max Roos, in the Schaerbeek section of Brussels, where he had picked up three men, according to Van Leeuw. There, authorities found about 33 pounds of the explosive material triacetone triperoxide, or TATP — a large amount. (By comparison, officials say the suicide belts used by the Paris attackers each contained less than a pound of TATP.)
At the house in Schaerbeek, investigators also found nearly 40 gallons of acetone and nearly 8 gallons of hydrogen peroxide. Acetone, a solvent found in nail polish remover, and hydrogen peroxide, found in hair bleach, are among the ingredients used to make TATP. The investigators also found detonators, a suitcase full of nails and screws, and other materials that could be used to make explosive devices.
In a trash can on the Rue Max Roos, investigators found a computer with Ibrahim el-Bakraoui's will. In the document, he said he no longer felt safe, did not know what to do and feared that if he dallied, he would end up in jail "next to him in a cell." It was not immediately clear if "him" referred to Salah Abdeslam, who was captured Friday and charged with terrorist murder over the Paris attacks.
As the investigation continued, Belgium remained in a state of mourning and on the highest state of alert. The nation observed a minute of silence at noon for the victims. The airport, which is being treated as a crime scene, is closed. Many subway lines were not running. The Maelbeek station, where about 20 people were killed, remained shut. Schools reopened, but many employees stayed home.
Prime Minister Charles Michel of Belgium said his country would show resolve. "The European values of democracy and of freedom are what was savagely assaulted by these tragic attacks," he said after meeting in Brussels with his French counterpart, Prime Minister Manuel Valls. Valls said: "Our two peoples are united in this hardship."
On Wednesday, the Belgian police raided a building in the Anderlecht neighborhood of Brussels. Officers in hazmat suits carted out files and plastic boxes from the building, while masked officers stood guard outside. Two police officers in the neighborhood said an arrest had been made, but the identity of the person arrested was not clear.
Since Friday, Belgian authorities have been searching for Najim Laachraoui, 24, a Belgian who has been linked to the Paris attacks in November. Whether Laachraoui was involved in the attacks Tuesday is not clear.
Several Belgian news outlets reported last week that the Bakraoui brothers had been wanted since the March 15 raid. It was not clear why authorities did not formally ask the public to help find them.
Ibrahim el-Bakraoui was sentenced to nine years in prison in 2010 for shooting at police officers after the attempted robbery of a currency exchange office; it was not clear when or why he was released.
In 2011, Khalid el-Bakraoui was sentenced to five years in prison for attempted carjacking; at the time of his arrest, he was in possession of assault rifles. Interpol issued an arrest warrant for him in August after he violated the conditions of his parole.
Khalid el-Bakraoui is believed to have used a false name to rent a safe house in Charleroi, Belgium, and the apartment in Forest. Fingerprints belonging to two of the Paris attackers, Abdelhamid Abaaoud and Bilal Hadfi, were found in the Charleroi house on Dec. 9, and Abdeslam's prints were found in the Forest apartment after the March 15 raid.
Speaking on Belgian radio Wednesday morning, Interior Minister Jan Jambon of Belgium said that police raids would continue, and that the threat status would remain at its highest level, 4.
"There are many hypotheses to put on the table," he said. "It's up to investigators to sort out fact from fiction."
Jambon discounted speculation that the attacks were reprisals for the arrest of Abdeslam, saying it was unlikely that terrorists "could have launched attacks of a scale seen yesterday in two, three days."
Speaking later to RTL radio, Jambon said it was also unlikely that the attacks could have been avoided even if Belgium had been at the highest threat level instead of Level 3, which was imposed after the Paris attacks.
"We were at Level 3; that means the probability is enormously elevated," he said, adding that Belgium had "everything possible in place to avoid a catastrophe like what happened yesterday, like other countries."
Jambon added, "A zero risk is not going to happen."
"Level 4 is when we have information that an attack will occur at a certain moment, in a certain place," he continued. "We did not have that information."
The Place du Grand Sablon, a handsome square in central Brussels that normally pulsates with tourists and shoppers seeking chocolates and luxury goods, was silent. Several shops were closed. At one cafe, the few customers were hunched over newspapers.
Under gray drizzle, the road in front of the Maelbeek subway station remained closed. Most employees of the European Union buildings in the area, which is usually bustling on a weekday morning, appeared to have stayed home.
"It's a scary situation," said Anton Zeilinger, an Austrian diplomat who lives and works nearby and who was at his office when the station was bombed on Tuesday. He said of the attackers, "A few bombs won't destroy the way we live, even if they want to."
Dozens of people continued to congregate at the Place de la Bourse to light candles and place flowers, drawings and other tokens of grief at a makeshift memorial in the middle of the square. Hundreds gathered at noon to stand in silence, before breaking into applause.
In the Eurostar lounge at the Gare du Midi, one of the main train stations in Brussels, passengers also observed a minute of silence at noon. Access to the station was permitted through just one entrance, and soldiers searched bags and luggage before allowing anyone in to buy tickets or to walk to the platforms. The subway lines that connect the train station to the rest of the city were closed.
Gilles de Kerchove, the European Union's counterterrorism coordinator, told the broadcaster RTBF that the apparent link between the Bakraoui brothers and Abdeslam suggested that the Brussels attacks were not the work of another active terrorist cell.
From a security perspective, that could mitigate the current threat, he suggested.
Brussels Airport said Wednesday morning that it was still determining when it could reopen, but that it would be closed at least through Thursday.
Areas like the Brussels Airport departure hall are particularly vulnerable because, like at most Western airports, bags are not searched until after check-in. That allows a would-be attacker to pack a bomb into a suitcase that could have far more space than an explosive vest and therefore be far more lethal.
In terrorism-plagued countries like Afghanistan and Iraq, and across the Middle East, bags are put through scanners when travelers enter the airport.
At least one of the bombs used in Brussels — the one at the airport — did far more damage and appears to have been far more powerful than those used in Paris, blowing out many of the windows in the large departure hall and shaking nearby buildings.