Turkish officials said Wednesday the country previously deported one of the suspected Brussels bombers, and authorities pressed the search for at least one other suspect in the deadly attack.
Belgium's chief prosecutor Frederic Van Leeuw earlier identified two brothers, Khalid and Ibrahim El Bakraoui, as suspected suicide bombers in the rush-hour attacks, which killed 31 people and injured at least 270. Ibrahim, 29, blew himself up at the city's Zaventem Airport, while Khalid, 27, detonated an explosive in the metro system, authorities said.
The so-called Islamic State claimed responsibility for the bombings, which came four days after police arrested Salah Abdeslam, a suspect in last year's Paris terror attacks, in Brussels. Tuesday's bombings rocked Belgium's capital and prompted reviews of security at airports and public transportation hubs around the world.
Authorities searched for 24-year-old Najim Laachraoui, who police sources named as a possible suspect, NBC News reported. It was not clear whether he was one of three men in an airport surveillance photo showing suspects.
Multiple reports Wednesday said Laachraoui, a suspected bombmaker in the Paris attacks, was the other airport suicide bomber. NBC News has not been able to confirm those reports.
At a news conference Wednesday, Van Leeuw said Ibrahim El Bakraoui was the man at the center of the surveillance image. An official in the Turkish president's office said El Bakraoui was caught at the Syrian-Turkish border in June and deported to the Netherlands, the AP reported.
The official corrected Turkish President Recep Tayyip Erdogan, who earlier said El Bakraoui was deported to Belgium. The official noted that Turkey warned both Dutch and Belgian authorities that El Bakraoui was a "foreign terrorist fighter," the AP said. Dutch officials later let him go free because Belgian officials could not establish ties to terrorism.
Van Leeuw did not confirm the identities of the two others in the photo.
Police on Wednesday were hunting for the person on the right of the image, wearing white and a dark hat, NBC reported. He abandoned a suitcase before leaving the airport Tuesday, NBC said, citing officials.
Earlier conflicting reports suggested he was Laachraoui, a suspected Islamic State bombmaker whose DNA was found on explosive belts used in the Paris attacks. Laachraoui previously used the false identity of Soufiane Kayal, the Belgian prosecutor's office said. That alias links him directly with Abdeslam.
Police knew the brothers, both born in Belgium, from previous criminal activity, Van Leeuw said. In 2010, Ibrahim was sentenced to nine years in prison for shooting at police with a Kalashnikov during a robbery. In early 2011, Khalid El Bakraoui was arrested for possession of Kalashnikovs and had been sentenced to five years in prison for carjackings.
Meanwhile, police detained one unidentified person in a raid on Tuesday evening in the Schaerbeek area of Brussels, according to the authorities. Another raid on Tuesday discovered 150 kilograms of explosives, detonators and a suitcase full of nails and screws. Police have also found what they believe is the suicide note of Ibrahim El Bakraoui.
On Sept. 9, 2015, Abdeslam was checked at the border between Hungary and Austria while driving a Mercedes. He was accompanied by two people using fake Belgian identity cards with the names of Samir Bouzid (Mohammed Belkaid, who was killed in a police raid in the Brussels neighborhood of Forest last week) and Soufiane Kayal, NBC said.
Belgian media added that Khalid, using a false name, had rented an apartment in Forest, where police were involved in the shootout last week.
As the search for the attackers continued, the Brussels Airport said Wednesday no passenger flights would come into or out of the facility until Saturday.
Separately on Wednesday, U.S. President Barack Obama offered Belgium "any assistance" in investigating the attacks. He pledged to defeat the so-called Islamic State in the wake of the latest attack.
"We will also continue to go after ISIL aggressively until it is removed from Syria and removed from Iraq and is finally destroyed," he added, referring to the terrorist group by an acronym.
Separately, the AP, citing multiple security officials, reported that ISIS has trained at least 400 attackers and sent them into Europe for possible attacks.
— NBC News, Reuters and The Associated Press contributed to this report.