The Columbus airport is joining its counterparts nationwide in training employees to recognize signs of human trafficking.

All 400 employees at Port Columbus International Airport will view a 30-minute video on spotting signs of trafficking beginning this month.

The video by the Ohio Department of Public Safety recommends keeping an eye out for people not allowed to speak for themselves, not in control of their travel documents or being closely watched or followed.

Last month, San Francisco International Airport trained about 220 employees who come in contact with the public, including baggage handlers and maintenance workers.

The Department of Homeland Security posted human trafficking awareness messages on video monitors and airport shopping bags at 13 airports last summer, including JFK and LaGuardia in New York, Chicago-O'Hare and Los Angeles International Airport.