Direct Terrorist Threat - Some 102,313 Syrians were granted admission to the U.S. - The Obama administration cannot be sure of the whereabouts of thousands of foreigners in the U.S. who had their visas revoked over terror concerns and other reasons, a State Department official acknowledged Thursday.

Some 102,313 Syrians were granted admission to the U.S. as legal permanent residents or through programs including work, study and tourist visas from 2012 through August of this year, a period which roughly coincides with the devastating civil war that still engulfs the Middle Eastern country. Experts say any fears that terrorists might infiltrate the proposed wave of refugees from United Nations-run camps should be dwarfed by the potential danger already here.

"The sheer number of people arriving on all kinds of visas and with green cards, and possibly U.S. citizenship, makes it impossible for our counterterrorism authorities to keep track of them all, much less prevent them from carrying out attacks or belatedly try to deport them," said Jessica Vaughan of the Center for Immigration Studies.

The Obama administration cannot be sure of the whereabouts of thousands of foreigners in the U.S. who had their visas revoked over terror concerns and other reasons, a State Department official acknowledged Thursday.