A former city employee pleaded guilty Monday to forging and selling fake SEPTA passes to City Hall workers, prosecutors said.

Mark Cooper, 35, worked for Philly 311, the city's Call Center. Federal prosecutors say he and his co-worker Kimberly Adams sold more than $10,000 worth of forged TransPass cards between August 2013 and June 2015.

The duo sold about 2,000 fake passes for about $50 apiece, prosecutors said. The passes - which allow unlimited monthly travel on buses, trolleys and subways - retail at $91 a month.

Prosecutors say Adams made a majority of the sales in and around City Hall, and targeted commuting municipal workers. Adams was tried separately and pleaded guilty in August 2015.

Cooper created the forged cards by replicating the magnetic strip found on the back of authentic passes with equipment he ordered off Amazon.com, investigators said.

Adams is scheduled to be sentenced May 18, and Cooper on Aug. 4. Both face up to 20 years in prison and fines of up to $500,000.

SEPTA officials declined to comment.