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.

The scanners resemble a small trunk on wheels. They can be pointed toward an escalator or a station entrance, and can scan people from 30 feet away without requiring people to line up or slow down.

"We will be looking at areas where we can screen large numbers of passengers with minimal inconvenience," Metro security chief Alex Wiggins said at Union Station on Tuesday.

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