Police are scouring Belgium for one of the bombers behind the Brussels attacks as European security chiefs meet in the city to discuss the fight against terrorism.
One of the attackers dubbed the "man in white" and pictured at the airport moments before twin explosions ripped through the building remains at large.
Belgium's threat alert is at its highest level and several other suspects who may be linked to the attacks are still on the loose, according to Paul Van Tigchelt, head of Belgium's terrorism threat body.
As the manhunt continues, Home Secretary Theresa May is expected to join counterparts from the European Union in Brussels for an emergency meeting on Thursday.
The meeting of justice and security ministers is "intended to show solidarity with Belgium, discuss the actual state of play in the fight against terrorism and pursue swift completion and implementation of legislation", the EU said.
Prosecutors said at least 31 people were killed and 270 injured in the three suicide bomb attacks at Zaventem Airport and Maelbeek station in Brussels on Tuesday morning, and the death toll could rise.
In a day of fast-moving revelations,it emerged on Wednesday that Najim Laachraoui, 24, the suspected bomb maker in the Paris terror attacks, was one of two suicide bombers who blew themselves up in the Brussels airport.
The revelation adds weight to the theory that both attacks, which killed more than 150 people and injured hundreds more, are linked to the same Islamic State cell.
Ibrahim El Bakraoui, who is also known as Brahim, and Laachraoui blew themselves up at the airport at 8am local time.
Just over an hour later more commuters were killed when Ibrahim's brother Khalid detonated a suicide bomb in the carriage of a train at the station.
Turkish officials have claimed they warned the Belgian authorities last summer that Ibrahim was "a foreign terrorist fighter" – but he was allowed to walk free.
He was caught in June last year at the Turkish-Syrian border and deported to the Netherlands, but they let him go after the Belgians failed to establish any links with terrorism, Turkey said.
One Briton remains missing and four others were injured in the attacks.
David Dixon, who is originally from Hartlepool but was living in Brussels, has not been heard from since the Metro explosion.