Brussels bomb suspect Najim Laachraoui is still on the run after the blasts which killed at least 31 people and left more than 200 injured.
An arrest in connection with the terror attack has reportedly been made in the Anderlecht suburb of Brussels, but local media reports that Laachraoui had been detained were later withdrawn.
The 25-year-old, who has been linked to the atrocities in Paris five months ago, is believed to have accompanied two men, brothers Khalid and Brahim El Bakraoui, to Zaventem Airport on Tuesday.
Khalid and Brahim El Bakraoui had been involved in organised crime, but had so far not been linked to terrorist activities, the broadcaster RTBF said, quoting unnamed police sources.
Broadcaster VRT reported that only one of the brothers is suspected of having been at the airport, while the other targeted the Maelbeek subway station.
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Bomb-maker Laachraoui is also suspected of having played a "decisive role" in the Paris terror attacks, French media has reported.
Laachraoui was already sought by the police since Monday, Belgian newspaper DH says.
His DNA had been found in houses used by the Paris attackers last year, prosecutors said on Monday, and he had travelled to Hungary in September with Paris attacks prime suspect Salah Abdeslam.
Laachraoui is also suspected of being responsible for the bombs used in the Paris massacre in November after his DNA was found on suicide belts used in the Bataclan Theatre and the Stade de France.
The two suicide bombers who struck at Brussels airport have been named by Belgian state broadcaster RTBF as brothers Khalid and Brahim El Bakraoui.
Citing a police source, RTBF said the brothers who were Brussels residents were known to the authorities but for involvement in organised crime rather than terrorism.
Khalid, under a false name, had rented the flat in the Forest borough of the Belgian capital where police killed a gunman in a raid last week, RTBF said.
Investigators found after that raid an Islamic State flag, an assault rifle, detonators and a fingerprint of Abdeslam's, who was arrested three days later.
Investigators are focusing on whether CCTV footage captured moments before the airport blasts shows two of the three suspected terrorists wearing single gloves to secrete detonators.
Zaventem's mayor said the explosives were stowed in their luggage and detonated before reaching the security gate.
