One of the suicide bombers who attacked the Brussels airport had previously worked as a cleaner at the European Parliament.
According to a parliamentary spokesman, Najim Laachraoui did not have a criminal record at the time of his employment.
“As a student, he held a summer holiday job cleaning at the parliament for one month in 2009 and one month in 2010,” the spokesman said in a statement.
“Those were the only instances he worked at the parliament.”
Najim Laachraoui blew himself up at the Brussels airport, and is also suspected of making suicide vests for last November’s Paris attack.
The revelation came as Belgium’s prime minister admitted the country had made mistakes in how it tackled violent extremism.
“In the fight against terrorism, in all countries in the world and in Europe, there have been successes and there have been failures,” Prime Minister Charles Michel said.
But he rejected suggestions Belgium had become a “weak link” in Europe’s war on terrorism.
“If we were weak, then we would not have been able to convict 100 persons,” he said, arguing that Belgian authorities had prevented many attacks.
He made the comments to an audience of largely foreign journalists following last month’s attack on the Brussels airport and metro.
The attacks killed 32 people, along with the three bombers.
Mr Michel says Belgium is determined to learn from its mistakes and improve information sharing between various security agencies.