Less than half the U.S.-Mexico border secured: report

Less than half of the United States' porous southwest border with Mexico is under the operational control of the U.S. Border Patrol, a government watchdog reported on Tuesday.

The study by the Government Accountability Office said that the Border Patrol had achieved "varying levels of operational control" over just 873 miles, or 44 percent, of the nearly 2,000-mile border by the end of last year.

The report found that the number of miles under operational control increased an average of 126 miles per year from 2005 through 2010.

The GAO, which is the investigative arm of the U.S. Congress, noted that only 129 of those miles, or 15 percent, were classified as "controlled" -- the highest level for detecting and arresting intruders.

Of the 1,120 miles of the border where operational control had not been achieved, around two-thirds were classified as "monitored," meaning that the Border Patrol had a high probability of detecting intrusions, although their ability to respond depended on the available resources.