Federal Agents have announced they intend to step up scrutiny on immigrants who have over-stayed their holiday visas.

Since earlier this year agents have been running overstayed-visas files through security, immigration and law enforcement databases, the Daily News reports.

The Department of Homeland Security has been attempted to deal with the millions of immigrants who have overstayed their holiday visas after at least four September 11 hijackers were found to be in the country with out-of-date visas.
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John Cohen, the department's principal deputy coordinator for counterterrorism said this is part of their screening for any immigrants who may be a considered a risk by national security.

Authorities began screening a backlog of 1.6 million visas earlier this spring. After running checks they found that 800,000 had either updated their visa status or left the country. They flagged 2,000 of the remaining visas for investigation for national security reasons.

The 9/11 commission have recommended the establishment of a biometric exit program which would effectively “log out” immigrants from the U.S. once they exit. However  Homeland Security said this would prove too expensive.