Illegal immigrants watch from behind a fence as police patrol the perimeter of a detention center at Amygdaleza, on the northern fringes of Athens, on April 30, 2012. Thanassis Stavrakis/AP hide caption

itoggle caption Thanassis Stavrakis/AP

Illegal immigrants captured in the Libyan coastal city of Surman are held at a temporary prison in an eastern district of Tripoli, Libya, on Oct. 19. Hamza Turkia/Xinhua /Landov hide caption

itoggle caption Hamza Turkia/Xinhua /Landov

A survivor of the shipwreck of migrants off the Italian island of Lampedusa looks out over the water Tuesday. The tragedy has bought fresh questions over the thousands of asylum-seekers who arrive in Europe by boat each year. Tullio M. Puglia/Getty Images hide caption

itoggle caption Tullio M. Puglia/Getty Images