Los Angeles County's rail system will be the first in the United States to deploy body scanners that can detect suicide vests and other improvised explosives, transportation officials said Tuesday.

Later this year, the Metropolitan Transportation Authority will deploy several portable scanners that can be moved to any of the system's 93 subway and light-rail stations. The devices will be used in response to terrorism threats, or to scan large crowds at a station near a protest or a sporting event, officials said.