WASHINGTON (Reuters) - U.S. authorities are facing a huge backlog of records involving people who have stayed in the United States after their visas expired, according to a report released on Tuesday, revealing that a security gap has not been fixed since the September 11, 2001 attacks.
The Department of Homeland Security's US-VISIT system had a backlog of some 1.6 million records of potential visa overstays as of January 2011, said the report by the U.S. Government Accountability Office, Congress' investigative arm.
Five of the 19 men who hijacked the planes in the September 11 attacks had overstayed their visas and the report found that some 36 of the 400 people who have been convicted on terrorism-related charges since 2001 had also stayed after their visas expired.
"It is simply unacceptable that we are still unable to systematically identify people who overstay -- some of whom may be terrorists waiting to attack innocent Americans," Joe Lieberman, an Independent who is chairman of the Senate Homeland Security Committee, said in a statement.
Some of the records may include duplicates because of computer system changes, may not have been reviewed yet, or include cases that are not necessarily considered to be a priority, the GAO report said.
Officials in charge of the US-VISIT program told the GAO that it had spent $3.7 million of the $5 million available to help deal with the backlog but that it needed more money, a tough task as the government is facing deep spending cuts.
As a matter of policy, records involving visa overstays of 90 days or less or those who are not deemed to pose a national security or public safety risk do not trigger an immediate lookout warning, according to the report.
U.S. officials prefer to focus on finding the more egregious violators who have stayed long beyond their visa expiration, the GAO said.
The report was released a day before Homeland Security Secretary Janet Napolitano is due to testify on border security before Lieberman's committee.
A spokesman for Napolitano said the agency gives priority to removing illegal immigrants who are a national security risk, are convicted criminals or pose other threats to public safety.
"We pursue overstay cases based on these priorities -- including by fully investigating 100 percent of overstay cases that have a nexus to national security and serious criminal acts," DHS spokesman Matthew Chandler said.
There are also other ways for U.S. officials to identify those who have entered the United States legally but have stayed longer than they were initially allowed and to remove them, according to the department.
Editing by Vicki Allen