The Transportation Security Administration began testing new technology Tuesday designed to detect explosive suicide vests at New York City’s Penn Station.

The TSA is testing two types of units in partnership with Amtrak. 

One resembles a white camera on a tall tripod, while the other is mounted inside a trunk.

The TSA has been working on the experimental devices, known as standoff explosive detection units, since 2004 with transit agencies. The technology has also been used to secure large events, like the 2014 Super Bowl, and was tested by the Los Angeles Metropolitan Transportation Authority in December. It hasn’t been deployed permanently at any transit hub because it’s still under development.

Unlike airport screening systems, the equipment projects scanning waves at people rather than having them walk through a scanner. 

The machines scan for metallic and non-metallic objects on a person’s body.

Back in December, authorities said attempted suicide bombing suspect Akayed Ullah tried to blow himself up near the Port Authority station, allegedly using a crudely made pipe bomb attached to his body.

“This technology would have been effective and would have identified the suicide bomber who was at the Port Authority,”  the TSA’s Lisa Farbstein told CBN News. “This specific technology will help us detect any artfully concealed items under clothing that could possibly be an IED, an improvised explosive device, such a suicide vest.”

Testing will evaluate the technology’s effectiveness at detecting bombs and the frequency of false alarms.