Washington, D.C. ? At least three dozen railroad workers may have been fired unfairly because they failed background checks recommended by the Homeland Security Department, Democratic congressmen said Thursday.

Civil rights activist Jesse Jackson and House Judiciary Chairman John Conyers, D-Mich., said Thursday they were trying to find out why railroad workers were told they were dismissed because of directives from the Transportation Security Administration, which is part of Homeland Security.

The use of background checks as a security measure has grown since the Sept. 11, 2001, terrorist attacks. Hundreds of thousands of airport workers, longshoremen, mariners and haz-mat drivers are subject to background checks before they’re issued the security badges or licenses necessary for them to do their jobs.

Jackson came Thursday to Washington to enlist support for the railroad workers, ex-felons who had clean employment records but were fired after background checks.

Many were hired under work-release programs, Jackson said.