The New York Police Department revealed Wednesday that it was developing a device that would scan people for concealed firearms on their body.

The Wall Street Journal reports Commissioner Raymond Kelly saying the NYPD is testing a T-ray (terahertz radiation) machine. Such technology is increasingly being used in airport scanners because the radiation is considered less harmful than X-ray. As IEEE Spectrum put it in its article a few years ago examining the technology, T-rays go through most materials but reflect off metal.

“If something is obstructing the flow of that radiation, for example a weapon, the device will highlight that object,” Kelly said at an event attended by the New York City Police Foundation, according to the WSJ.

NYPD Tests T Ray Machine to Detect Concealed Firearms

The image on the left is what the technology sees. (Photo: NYPD via DNA Info)

WSJ says NYPD spokesperson Paul Browne said the “multimillion” device was funded by the U.S. Department of Defense. Unlike, large X-ray scanners, recent research has shown the T-ray device, for which official deployment by the NYPD was not specified, could someday be small enough for the officers to carry around.

NYPD Tests T Ray Machine to Detect Concealed Firearms

This is the size of the device being tested by the NYPD now but they hope to make one small enough to be hand-held by an officer. (Photo: NYPD via DNA Info)

DNA Info reported Kelly saying the device is “still very much in the testing phase, but we’re certainly encouraged by the developments that we’ve seen.” It noted that the technology was received last week and tested from a truck.

Given the potential of such a device to review items on a person’s body without their knowledge, Kelly told the audience that the city was working with lawyers to figure out how it could be used lawfully.

Kelly said the device was developed with the London Metropolitan Police and a manufacturer in the U.K.

In addition to T-ray scanners being used for security measures, the technology is also being researched in the medical industry as well. According to a study published last year, T-rays can sense certain molecules based on a specific THz range that could identify cancerous tumors, for example.

Watch this Discovery report on T-ray scanners:

(H/T: The Verge)