Homeland Security Secretary Janet Napolitano affirmed that security at the U.S.-Mexico border is tighter than ever and encouraged a more comprehensive approach to immigration report in an interview with ABC News on Thursday.

"We're putting mobile surveillance so that we can move around and watch and we have increased the boots on the ground," she said. "Over the last couple of years, we've added what we call boots in the air, aerial surveillance, for the first time, border-wide."

Napolitano said the bulk of those improvements had been made in the sector of the border near Tucson, Arizona. With the amount of technology and manpower committed to the area, she said, the country's entire approach to undocumented immigration needed to be addressed.

"From my standpoint, one of the biggest draws of illegal traffic across the border is the demand for illegal labor," she said. "And until you have a natural -- a nationwide system, for employers to be able to verify their employees, it's really tough to get at that demand side."

Napolitano's remarks echoed calls from immigrant rights advocates to hold off on devoting more resources to security in the wake of a net-zero immigration rate from Mexico and record amounts of deportations and focus on crafting an approach that can help the 11 million undocumented immigrants in the U.S. work toward citizenship.

A plan leaked by President Barack Obama's administration on Feb. 16 included measures increasing the amount of immigration judges and the expansion of the "E-Verify" system allowing more employers to track workers' immigration statuses, while calling for the creation of a "Lawful Prospective Immigrant" visa for qualified applicants.

Napolitano also said she was surprised the release of thousands of undocumented immigrants from federal detention centers.

The Associated Press reported on Friday that 2,000 immigrants had been released from facilities in Arizona, California, Georgia and Texas in a move spurred by government spending cuts.

"Detainee populations and how that is managed back and forth is really handled by career officials in the field," she said. "Do I wish that this all hadn't been done all of a sudden and so that people weren't surprised by it? Of course."

[Image via Agence France-Presse]