The New York Police Department, with assistance from the Pentagon, is testing a scanning device that can remotely detect concealed firearms, Police Commissioner Ray Kelly said Tuesday.

The device measures natural radiation emitted by people and can detect when this flow of energy is impeded by an object, such as a gun.

"This technology has shown a great deal of promise as a way of detecting weapons without a physical search," Kelly said in a speech before a police group in Manhattan.

Known as terahertz imaging detection, the technology functions similarly to night-vision goggles, which detect infrared radiation. But unlike much infrared radiation, the terahertz wavelength is not blocked by clothing.

"With terahertz, you will be able to identify a gun as a gun," said John Federici, a physics professor at the New Jersey Institute of Technology.