Chicago police investigate fire on CTA train in the Loop

CHICAGO - A man started a fire on a CTA train in the Loop Saturday morning before fleeing, Chicago police say. 

Police responded to the Harold Washington Library station at State and West Van Buren Streets at 12:54 a.m. 

An unknown male offender started a fire on a rail car, causing minor damage. 

The station services the Brown, Orange, Pink and Purple lines. 

The Arson unit is investigating.