CHICAGO — Police are investigating after a man was stabbed on the CTA Red Line’s Roosevelt platform early Saturday morning.

Chicago police said a 40-year-old was in a “physical altercation” with a man on the 1100 block of South State Street around 4:40 a.m. when the man took out a sharp object and stabbed the 40-year-old in the back.

The suspect fled the scene and the 40-year-old was taken to Northwestern Hospital in fair condition.

No one has been taken into custody and Area Three detectives are investigating.

Earlier that same morning, a CTA employee was found found on the Brown Line train tracks in the Loop.