Belgian media which earlier reported the arrest on Wednesday of a prime suspect in Tuesday's bomb attacks in Brussels said the person detained was not, in fact, Najim Laachraoui.
The subject of the conflicting reports, Laachraoui, 25, is believed to be the man seen on CCTV pushing a baggage trolley alongside two other bombers and then running out of the airport terminal.
Laachraoui is wanted in connection with the Paris attacks.
His DNA was found on almost all of the explosives belts used in those attacks and at a Brussels hideout used last week by prime Paris suspect Salah Abdeslam, who was arrested last Friday after a shoot-out with police.