The two suicide bombers who attacked Brussels airport were reportedly listed in US databases as potential terror threats.
NBC News said that according to US officials, Khalid and Ibrahim El Bakraoui were known to US counter terrorism authorities prior to Tuesday morning, when the pair and a third man devastated the Belgian capital.
The officials would not say on which of the many US terrorism databases the brothers were listed.
But the disclosure does raise questions about how Belgian authorities could describe the men simple as petty criminals who were not on their counter-terrorism radar, the network said. It also raises questions about the extent to which Western nations are effectively sharing information that could prevent attacks.
The security lapses in a country that is home to the European Union and Nato have drawn international criticism of an apparent reluctance to tackle Islamist radicals effectively.
The Associated Press said that the Dutch justice minister on Thursday confirmed that one of the Brussels suicide bombers was flown from Turkey to Amsterdam in July, but said that authorities were not told why and had no reason to detain him.
In a letter to parliament, Justice Minister Ard van der Steur said that Ibrahim El Bakraoui was put on a plane from Istanbul to the Dutch capital on July 14, but that Turkish officials did not say why and his name wasn't flagged in any Dutch law enforcement databases.
Mr Van der Steur said that El Bakraoui had a valid Belgian passport when he arrived in Amsterdam “so there was no reason to take any action” at Schiphol Airport. It wasn't clear what El Bakraoui did after arriving in the Netherlands.
President Recep Tayyip Erdogan said on Wednesday that El Bakraoui, was caught in June 2015 near Turkey's border with Syria and deported, at his own request, to the Netherlands, with Ankara warning Dutch and Belgian officials that he was a “foreign terrorist fighter.”
Brussels Interior Minister Jan Jambon and Justice Minister Koen Geens tendered their resignations to Prime Minister Charles Michel, who asked them to stay on. “In time of war, you cannot leave the field,” sad Mr Jambon, a right-wing Flemish nationalist.
The two attacks killed at least 31 people and injured hundreds.
