BRUSSELS — Belgian authorities have raided dozens of homes and arrested 12 suspects in a major anti-terror investigation which they said required “immediate intervention.”

The federal prosecutor’s office said Saturday that homes and car ports were searched in 16 municipalities, mostly in and around Brussels.

The statement said 40 people were taken for interrogation, of which 12 were arrested. It said there were no major incidents during the raids and that no arms or explosives were found.

The operation comes as Belgium remains under the second highest terror alert in wake of the March 22 attacks on the Brussels subway and airport which left 32 people dead.

Authorities are also especially attentive to security risks during the ongoing European soccer championships in neighboring France. Belgium played Ireland Saturday afternoon and big gatherings to watch the game were planned across the nation.