They shared a picture of the suspects, who police say beat a man with a skateboard last Thursday night at the Damen Street Station.
Police say the suspects implied that they had a knife and choked the victim while taking his belongings.
Police remind everyone to always be aware of your surroundings and to report suspicious activity immediately. If you are confronted by an assailant, they say to remain calm and try to remember unique physical characteristics. Police also say to never pursue a fleeing assailant.
Anyone with information is asked to call the Mass Transit Investigations at (312) 745-4443.