"The indications that led to the arrest of Faycal Cheffou were not substantiated by the ongoing inquiry. As a result, the subject has been released by the examining magistrate," the federal prosecutor's office said in a statement, without giving further details.
Belgian media had identified the man as Faycal Cheffou who claimed to be a freelance journalist.
Cheffou was charged on Saturday with "taking part in a terrorist group, terrorist murder and attempted terrorist murder".
A source close to the inquiry previously told AFP that prosecutors were looking into the theory that he was the third man seen in CCTV footage alongside two suicide bombers at Zaventem airport.
Belgian police earlier on Monday released some of the CCTV images in a bid to identify the suspect.
In the video, a man in a hat and white jacket is seen pushing a trolley with a large bag through the departure hall next to bombers Ibrahim El Bakraoui and Najim Laachraoui.
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