Homeland Security still doesn’t have a mechanism in place to track when, and if, legal foreign visitors leave the country, a recent Government Accountability Office report found.

The inability to track “visa overstays” is listed among the remaining work left for the Department of Homeland Security in the GAO’s progress report about efforts 10 years after the terrorist attacks of Sept. 11, 2011.

The department has implemented a program to take and electronically store biometric and biographic information for all foreign visitors entering through ports of entry with a visa, but it has still not created a similar program to track when those people leave the country.

For example, when a Mexican man with a student visa enters the country through the Nogales Port of Entry in Arizona, his fingerprints and photo are taken and put in a computer system. But, when he or she leaves the country through the same port, there is no system in place to “sign out,” if you will.

Homeland Security has a plan is in place to create a formalized exit program, but it has not yet been created, the GAO reported. One major hurdle is that there would be significant costs to such a plan because land ports of entry are not currently built for this process, the GAO found in an in-depth April 2011 report on the visa overstay issue.

There is no concrete data on how many people who overstayed visas are living in the U.S. but the Pew Hispanic Center estimated in 2006 that there were 4 to 5.5. million, which represented 33-45 percent of the then-12 million illegal immigrants in the United States. The illegal immigration population has since dropped to 11.2 million, the Pew Hispanic Center reported this year.

Visa overstays are a terrorism concern as well. Five of the 19 hijackers from the Sept. 11, 2001, terrorists attacks had overstayed legal visas, the GAO reported. And about 36 of the 400 people convicted by the Department of Justice in terrorism-related investigations had overstayed legal visas, the GAO reported.

In addition to not being able to track visa overstays, the federal government has difficulty finding and deporting this category of illegal immigrants, the GAO reported:

• Homeland Security arrested about 8,100 visa overstayers from fiscal year 2004 to 2010. That’s a fraction of the estimated 4 to 5.5. million people who are in the U.S. after overstaying a visa.

• Homeland Security has closed about 34,700 overstay investigations from fiscal year 2004 to 2010.

• Immigration and Customs Enforcement, an agency withing Homeland Security, has devoted about 3 percent of its investigative work hours to overstay investigations since fiscal year 2006.

Each year, millions enter the country legally with visas.

The State Department issued more than 36 million non-immigrant visas from fiscal year 2005 to 2010, four-fifths of which went for business travel, pleasure, tourism, medical treatment, or for foreign and cultural exchange student programs, the GAO found.