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SALT LAKE CITY -- The Department of Homeland Security and the Transportation Security Administration are defending full-body scanners at airports, a year after the Christmas Day "underwear" bomber's plot fizzled in Detroit.
A new study points to a flaw in the scanners' capabilities.
These scanners are great when it comes to detecting blocks of explosives. But a study in Journal of Transportation Security says when it comes to even large amounts of explosives molded into thin layers, they're "invisible," practically looking the same as human flesh.
The authors of the study are medical imaging experts at the University of California-San Francisco. They say the scanners are not a guarantee of security.
But over the weekend, the TSA and Homeland Security went on the defensive, with the TSA saying "advanced imaging technology is highly effective in detecting non-metallic threats."
Homeland Security Secretary Janet Napolitano joined CNN's "State of the Union."
"Our job is not only to react, but to be thinking always ahead, what could be happening," she said.
Security has been changed and increased since the "underwear bomber" tried to set off explosives on a flight from Amsterdam to Detroit.
In addition to the scanners and "enhanced" pat-downs, planes are kept far away from terminals now.
We saw that in Salt Lake on Oct. 28 when a bomb threat was called in on a flight from Helena, Mont. That plane was kept at the far north end of Salt Lake City International.
Homeland security says the full-body scanners are going nowhere for the "foreseeable" future. There are currently 486 scanners across 78 airports, and the plan is to double that number by the end of 2011.