Belgian soldiers gesture for vehicles to keep a safe distance as they patrol near a court building where Salah Abdeslam, the top suspect in last year's deadly Paris attacks, was expected to appear before a judge in Brussels, March 24, 2016.

A soldier stands guard at the entrance of the closed De Brouckere metro station, March 24, 2016, in Brussels.

Luggage that was collected from the planes which were on the tarmac at the time of the attacks is seen March 24, 2016 in a Brucargo building in Steenokkerzeelas, Brussels.

Belgian soldiers search passengers before they board the Brussels Metro after terror attacks on March 23, 2016 in Brussels.

Forensics officers work in front of the damaged Zaventem Airport terminal in Brussels, March 23, 2016.

A flight schedule board is seen through broken windows inside the terminal at Brussels International airport following bomb attacks in Brussels metro and Belgium's airport of Zaventem, Belgium, March 23, 2016.

Soldiers and police carry out checks at the Central Station in Brussels on March 23, 2016, a day after blasts hit the Belgian capital.

Belgium police leave after an investigation in a house in the Anderlecht neighborhood in Brussels, Belgium, March 23, 2016, one day after deadly suicide attacks on the Brussels airport and its subway system.

Turkish police with a K-9 dog search luggage in an area at Ataturk Airport in Istanbul, Turkey, March 23, 2016.

Heavily armed British police stand outside the Belgian embassy in London, March 23, 2016.

Coroners transport a body out of a metro station in Brussels on March 23, 2016, a day after the station and the Brussels-Zaventem airport were attacked with bombs.

Fallen bricks from a wall in a car park are seen following an explosion at Maelbeek metro station following attacks, March 22, 2016 in Brussels, Belgium.

People stand at a security checkpoint at Brussels South railway station following the explosions, March 22, 2016.

An Amtrak police K-9 unit patrols Union Station, March 22, 2016 in Washington. Security has been increased around the city after bombings in Brussels.

An empty Rue Royale (Koningstraat) which leads to the Palais de Justice following explosions in Brussels on March 22, 2016. The Islamic State group officially claimed responsibility for the attacks in Brussels that left 34 people dead.

A soldier surveys the damage at Zaventem airport in Brussels, Belgium March 22, 2016.

Belgian Federal Police released this image showing the suspects of this morning's attacks at Brussels Airport, in Zaventem, March 22, 2016.

Belgian Prime Minister Charles Michel visits the site of the terrorist attack at the metro station in Maelbeek, Brussels, Belgium, March 22, 2016.

Broken glass litters the ground at an entrance to the Maelbeek metro station following todays attack, March 22, 2016 in Brussels, Belgium.

Forensic staff leave the Malbeek metro station in Brussels, March 22, 2016.

A woman puts a Belgian flag at a makeshift memorial at Place de la Bourse (Beursplein) following attacks in Brussels on March 22, 2016.

A policeman stands guard at the Midi train station following bomb attacks in Brussels, Belgium, March 22, 2016.

Police man a security checkpoint outside the Midi train station following bomb attacks in Brussels, Belgium, March 22, 2016.

Belgian soldiers and police stand at a cordon set to limit the number of people allowed into the central Station in Brussels on March 22, 2016 following co-ordinated attacks at the Airport serving the Belgian capital and its Metro system.

Two soldiers from the Belgian Army patrol outside EU headquarters as EU flags fly at half mast after explosions in Brussels on March 22, 2016.The attack prompted a lockdown of the Belgian capital.

Thousands of passengers are evacuated from Brussels airport March 22, 2016 after a terrorist attack at the airport.

Hearses are seen parked outside Brussels Airport in Zavedam following twin blasts on March 22, 2016.

A departures board at the airport in Barcelona, Spain informs travelers of the cancellation of flights to Brussels following attacks in the Belgian capital, March 22, 2016.

A video frame grab shows metro commuters being evacuated from a subway train in Brussels, after an explosion at the Maalbeek station. A series of apparently coordinated explosions ripped through Brussels airport and a city metro station March 22, 2016.

An injured person is evacuated by emergency workers at the scene after an explosion in a main metro station in Brussels, March 22, 2016.

Rescue teams evacuate wounded people outside the Maalbeek metro station in Brussels on March 22, 2016 after a blast at this station located near the EU institutions.

Brussels Policemen took up positions outside the Maelbeek metro station in Brussels, Belgium, on March 22, 2016.

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An injured man lies on the floor in Brussels Airport after explosions rocked the terminal March 22, 2016.A terrorist attack left a number dead in explosions that ripped through the departure hall at Brussels airport Tuesday, police said.

An injured woman leaves the scene at Brussels airport, in Brussels, March 22, 2016.

Rescue workers treat victims outside the Maelbeek underground station after a blast in Brussels, Belgium, March 22, 2016. This image taken from television video.

Travelers stand in a smoke filled terminal at Brussels Airport, in Brussels after explosions, March 22, 2016.

A traveler lies on the ground in a smoke filled terminal in a smoke filled terminal at Brussels Airport, in Brussels after explosions, March 22, 2016.

Travelers stand in a smoke filled terminal at Brussels Airport, in Brussels after explosions, March 22, 2016.

Two women wounded in Brussels Airport in Brussels, after explosions were heard, March 22, 2016.

Firefighters arrive at a security perimeter set in the Rue de la Loi near the Maalbeek subway station, in Brussels, March 22, 2016.

An image shared on Twitter shows the inside of the Brussels airport after a blast on March 22, 2016.

Broken windows are seen at the scene of explosions at Zaventem airport near Brussels, Belgium, March 22, 2016.

People react as they walk away from Brussels airport after explosions rocked the facility in Brussels, Belgium Tuesday March 22, 2016.

A victim receives first aid on March 22, 2016 near Maelbeek metro station in Brussels, after a blast at this station.

People in thermal blankets are driven from the scene of explosions at Zaventem airport near Brussels, Belgium, March 22, 2016.

A security perimeter has been set, on March 22, 2016 near Maelbeek metro station in Brussels.