One of the men who carried out the devastating bomb attacks in Brussels once worked as a cleaner at the European Parliament, officials say.
He had month-long summer jobs there in 2009 and 2010, the EU Parliament said, without revealing his identity.
Sources, however, say he is Najim Laachraoui, one of the airport bombers.
The Belgian prime minister has defended his country’s approach to fighting terror threats, insisting Belgium is not a “failed state”.
Charles Michel said everyone in authority had to take a share of the blame for failings before and after 22 March.
The attacks by so-called Islamic State on a Brussels airport and metro station killed 32 people.
Laachraoui, already a major suspect on the run after the Paris attacks in November, was named as one of the two bombers who targeted Zaventem airport.
The EU Parliament said the cleaning firm had provided proof that the person hired had no criminal record at the time.
The BBC’s James Reynolds in Brussels says the capital’s metro and its airport are gradually reopening.