A person of interest was in custody on Wednesday after a 26-year-old woman was set on fire and left in critical condition while riding a Chicago L train in the city’s busy Loop area earlier this week, the authorities said. The police did not name the person of interest, and said they were still investigating.

Federal terrorism charges have been filed against a suspect who allegedly lit a 26-year-old woman on fire on a Blue Line CTA train in the Loop.