Belgian police detained six people Monday in connection with an unsuccessful attack last year on a train enroute from Amsterdam to Paris.
Federal prosecutors in the the Western European country said the detainees are being questioned and a judge would decide whether they should remain in custody.
Six homes in the area of the capital city of Brussels were searched. No arms or explosives were found.
The terror level in Belgium remains at the second highest level after authorities charged three men Saturday with terror related crimes.
The men were suspected of planning attacks in Brussels on fans watching Belgium's Euro 16 soccer match in public places. That terror level means the threat of an attack "is possible and likely."
The charges were filed after weekend raids led to the detention of 40 people in a major investigation.
The prosecutor's office said no additional information will be released about the six detainees or the items taken in the searches.