Flemish public broadcaster VTM reported that of the 40 people questioned, 12 were taken into custody for potentially planning attacks in Brussels during a soccer match featuring Belgium’s national team.
The soccer tournament is held in France, where 130 people were killed in November during multiple assaults for which the Islamic State claimed responsibility.
Some of those who participated in those attacks were traced to Belgium, a country that has been on guard since a two-pronged attack in March killed 32 people in the country’s main airport and a crowded subway.
Both countries have remained vigilant amid high security during the European championship soccer tournament.
Belgian Prime Minister Charles Michel, who gave few specifics about the arrests, said an attack inside his country was “possible and likely,” according to the Associated Press.
“We are extremely vigilant, we are monitoring the situation hour by hour and we will continue with determination the fight against extremism, radicalization and terrorism,” Michel said.