A 26-year-old woman is fighting for her life after being set ablaze by a man during a heated dispute aboard a Chicago transit train on Monday night.

The shocking event unfolded shortly before 9:30 p.m. on the Chicago Transit Authority’s Blue Line downtown loop, according to WBBM.

Authorities have detained a person of interest, though no charges have been pressed so far, police confirmed.

Eyewitnesses recounted that as the train reached the Clark/Lake subway station, a confrontation erupted between the woman and a man, approximately 45 years old. During the altercation, he doused her with a liquid and ignited it.

Fleeing the scene, the man left the woman ablaze. She managed to exit the train but collapsed after running, still engulfed in flames.

Onlookers rushed to assist her and extinguished the flames before emergency personnel arrived. She was transported to Stroger Hospital with critical burns to her head and face, as reported by WGN.

“This woman was saved by a number of good Samaritans on the train with her,” Alderman Brendan Reilly said.

Police said the man in custody may be connected to a fire outside City Hall last week, WBBM said.

No further information about the incident was released, but police told WMAQ the investigation “remains ongoing.”