Two people were taken in for questioning following a house search today in Brussels, the prosecutor's office said.
Last evening, a building in central Brussels was searched on orders from an anti-terrorism judge. Two brothers and a friend were detained.
The prosecutor's office, without giving details, said an analysis of phone records led to yesterday's search. Authorities said they found no weapons or explosives at either residence, and did not identify those detained.
After a "thorough interrogation" by federal judicial police, the investigating judge ordered the release of all five, the prosecutor's office said. Eight other people detained earlier in Belgium in connection with the November 13 attacks in the French capital remain in preventive custody.
More From This Section
The Islamic State group claimed responsibility for the Paris attacks, which left 130 people dead.
A European Union summit last week resolved to continue the EU's effort against violent extremism, and called for wide-ranging measures including systematic checks on people crossing Europe's external frontiers.
In France, people travelling on high-speed trains from France to Belgium and the Netherlands now must pass through new metal detectors.
The open French-Belgian border has been under special scrutiny since the attacks by extremists with ties in both countries. In August, a Paris-bound Thalys was the scene of a thwarted attack when passengers subdued an Islamic extremist gunman who had boarded in Brussels.