The Los Angeles subway system is introducing a body-scanning device to be used for screening passengers.

The devices will be the first in one of the nation's subways to screen for explosive devices and weapons.

The L.A. County Metropolitan Transportation Authority partnered with the TSA on the screening system.

The portable system is designed to detect suicide vests and other hidden improvised explosives which are meant to cause mass casualties.

According to the MTA and TSA, it can screen both train and bus commuters without slowing foot traffic.

Officials say they tested the screening devices for a whole year prior to their deployment.