The TSA began a new screening policy for paper products at airport checkpoints in Missouri last month, and now the agency's branch in Sacramento, California, is testing out more invasive searches for books and food items.

In the new system, passengers are required to take all reading material and food out of their carry-on luggage and place it in a separate bin. TSA screeners can "fan" through travelers' books to see if anything is hidden in the pages, but agency officials insist they will not pay attention to the content. Critics have long argued passengers selected for extra screening are not chosen as randomly as the TSA claims, and book content — particularly of a political or religious nature — could re-ignite that debate.

"It's always been a series of insults," said Julie Sze, a University of California, Davis, professor who experienced the test procedure at Sacramento. "Books, magazines, food, those are like my three treasured things. It feels personal on a whole different level."

Department of Homeland Security Secretary John Kelly said Sunday he will likely expand the new searches nationwide and may also ban laptop carry-ons for all international flights in and out of the United States. Bonnie Kristian