Belgian prosecutors on Monday released a man they had charged in connection with last week's deadly Brussels bombings, saying they did not have enough information to justify holding him.
The man, named only as Faycal C, had been accused of taking part in the activities of a terrorist group and actual and attempted terrorist murder after being detained on Thursday.
His home had been searched but no weapons or explosives had been found.
The announcement was a major blow to an investigation that had netted half a dozen people charged with lesser offences in Belgium and others in the Netherlands, Italy and France, where officials said the same network had planned another attack.