People put candles on painted hearts with the Belgian colors to mourn for the victims at the place de la Bourse in the center of Brussels, Tuesday, March 22, 2016. Bombs exploded at the Brussels airport and one of the city's metro stations Tuesday, killing and wounding scores of people, as a European capital was again locked down amid heightened security threats. (Martin Meissner / AP)
People holding a banner reading "I am Brussels" behind flowers and candles to mourn for the victims at Place de la Bourse in the center of Brussels, Tuesday, March 22, 2016. Bombs exploded at the Brussels airport and one of the city's metro stations Tuesday, killing and wounding scores of people, as a European capital was again locked down amid heightened security threats. (Martin Meissner / AP)
The Belgian flag is projected on Rome's historical Trevi Fountain to honor the victims of the deadly attacks at Brussels airport and subway, Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and its subway system prompting a lockdown of the Belgian capital and heightened security across Europe. (Andrew Medichini / AP)
Belgian Prime Minister Charles Michel, left, and Belgium's Interior Minister Jan Jambon prepare to address a media conference in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. (Geert Vanden Wijngaert / AP)
People mourn for the victims at Place de la Bourse in the center of Brussels, Tuesday, March 22, 2016. Bombs exploded at the Brussels airport and one of the city's metro stations Tuesday, killing and wounding scores of people, as a European capital was again locked down amid heightened security threats. (Martin Meissner / AP)
Police stand outside a metro station after an explosion in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. (Geert Vanden Wijngaert / AP)
People light candles at a memorial set up outside the stock exchange in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. (Geert Vanden Wijngaert / AP)
People hold hands in solidarity near a memorial to attack victims outside the stock exchange in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. (Geert Vanden Wijngaert / AP)
Members of the German foreign ministry's crisis center work in Berlin on Tuesday March 22, 2016. Security was tightened across Europe and transport links paralyzed after a series of apparently coordinated explosions ripped through Brussels airport and a metro station. (Odd Andersen / AP)
Smoke billows from the Zaventem Airport after a controlled explosion, in Brussels, Tuesday, March 22, 2016. Bombs struck the Brussels airport and one of the city's metro stations Tuesday, killing and wounding dozens of people, as a European capital was again locked down amid heightened security threats. (Michel Spingler / AP)
People walk away from the broken windows at Zaventem Airport in Brussels after an explosion on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. At least 26 people were reported dead. (Geert Vanden Wijngaert / AP)
Police and rescue teams are pictured outside the metro station Maelbeek in Brussels, Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and its subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. (Martin Meissner / AP)
People walk away from the broken windows at Zaventem Airport in Brussels after an explosion on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. At least 26 people were reported dead. (Geert Vanden Wijngaert / AP)
A man looks at flowers and messages outside the stock exchange in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. At least 26 people were reported dead. (Geert Vanden Wijngaert / AP)
A woman places candles in the shape of a heart outside the stock exchange in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. At least 26 people were reported dead. (Geert Vanden Wijngaert / AP)
A man walks by solidarity messages written in chalk outside the stock exchange in Brussels on Tuesday, March 22, 2016. Explosions, at least one likely caused by a suicide bomber, rocked the Brussels airport and subway system Tuesday, prompting a lockdown of the Belgian capital and heightened security across Europe. At least 26 people were reported dead. (Geert Vanden Wijngaert / AP)
France's President Francois Hollande, center, shakes hands with Belgium Ambassador to France Vincent Mertens de Wilmars, outside the Belgium embassy, in Paris, Tuesday, March 22, 2016. Bombs exploded at the Brussels airport and one of the city's metro stations Tuesday, killing and wounding dozens of people, as a European capital was again locked down amid heightened security threats. The Islamic State group claimed responsibility for the attacks. At right is French foreign minister Jean-Marc Ayrault. (AP Photo/Thibault Camus) ORG XMIT: XTC108 (Thibault Camus / AP)
Terrorists set off at least two bombs in Brussels, Belgium, killing more than 30 and injuring dozens more.