CHICAGO (WOWO)— A person of interest is in custody after a woman was set on fire during a violent confrontation aboard a CTA Blue Line train late Monday night, according to Chicago police.

The attack happened just before 9:30 p.m. as the westbound train approached the Clark and Lake station in the Loop. Police said the victim, a 26-year-old woman, became involved in an argument with a man while riding in the same train car.

According to investigators, the dispute escalated into a physical altercation. During the struggle, the man reportedly poured an unknown liquid on the woman and then ignited it, setting her on fire in front of other passengers.

When the train pulled into the station, the assailant ran off while the woman stumbled out of the car and collapsed on the platform. Witnesses described a chaotic scene as commuters rushed to help extinguish the flames.

“This woman was saved by several good Samaritans on the train with her,” Ald. Brendan Reilly of the 42nd Ward said, praising the passengers who intervened.

By the time fire crews arrived, the flames were out, but the victim had suffered severe burns to her face and body. A witness told reporters the woman was in visible agony as she waited for help.

“I just saw her lying on the ground. She was hyperventilating and in a lot of pain — she was really in bad shape,” the witness said.

Paramedics transported the woman to Stroger Hospital, where she remains in critical condition.

Police said the person believed responsible is a man around 45 years old. A person of interest was taken into custody early Tuesday; however, officials have not released additional details about their identity or what may have triggered the altercation.

Detectives continue to investigate and are reviewing surveillance footage from the train and station. CTA officials say they are cooperating fully with the investigation.