Woman set on fire on Chicago train after man pours fluid on her and ignites it

A witness described the aftermath of the harrowing event, saying the woman appeared to be in an "awful lot of pain."

Editor's Note: A person of interest was taken into custody Tuesday afternoon. Our latest update can be found here. Our original story continues below.

A woman is in critical condition after police said she was set on fire while riding a busy Chicago train in Monday night, with lines shut down for hours and authorities searching for the suspect.

At about 9:25 p.m., a 26-year-old woman was riding the CTA Blue Line train near Clark and Lake Streets when she got in an argument with a man believed to be 45 years old. The altercation escalated and became physical, police said, and the man poured a liquid onto the woman and ignited it, setting her on fire.

The train then came to a stop and the man fled the scene, police added.

The woman then stumbled out of the train and collapsed, authorities said. She sustained severe burns to the body and was transported by the Chicago Fire Department to a nearby hospital where she was last listed in critical condition.

According to police, the fire was out by the time authorities arrived.

Videos and photos from the scene showed a large police and fire response at the Clark and Lake CTA station in the Loop, with firemen walking in and out of the station that houses the Blue, Pink, Brown, Orange Green and Purple Lines.

As train passengers walked by, paramedics could be seen loading the badly burned woman into an ambulance.

A witness described the aftermath of the harrowing event, saying the woman appeared to be in a "really bad state."

"I just saw a lady that was laying in the ground, and they were trying to give her CPR," the witness said. "And she looked like she was in an awful lot of pain."

At about 1:30 a.m., service resumed on the Blue Line, according to the CTA, with trains running on schedule as of Tuesday morning.

No one was in custody, and arson detectives from the Chicago Police Department were investigating, officials said.