U.S. Government officials have been unable to locate some 6,000 foreign nationals who have entered the United States on student visas.

According to ABC News, U.S. immigration officials have had difficulty keeping track of the escalating number of foreign students entering the United States. More troubling still, 58,000 students overstayed their visas in the past year alone.

ABC news also reports that, since the 2001 terrorist attacks, 26 student visa holders have been arrested in the United States on terrorism-related charges. The 9/11 Commission has in the past recommended that the student visa program be tightened to help eliminate future threats, but the system remains susceptible to abuse.

At present, there are 9,000 higher learning institutions that are on a government-approved list that certifies them to accept overseas applicants. Congress has raised concerns, however, that immigration officials have continued to grant schools certification even when they lack proper accreditation or state certification.

One school on the approved list, MicroPower Career Institute – licensed by the state of New York – saw five of the its top officials, including its president, indicted on charges of visa fraud in May. According to the indictment, 80% of the foreign students enrolled at MicroPower failed to meet attendance requirements, putting them out of compliance with their visas. MicroPower did not report the attendance discrepancies and all five school officials have pleaded not guilty in the case.

Universities are responsible for keeping track of their student visa holders and are required to report to government officials if students fail to attend class. There are concerns, however, that a number of institutions have been too focused on selling visas.

Despite repeated delay, ICE Homeland Security Investigations seems keen to tighten the student visa protocol.