Chicago police say a 41-year-old woman was attacked Monday by a man after boarding CTA Blue Line. View Full Caption Chicago Police Department

CHICAGO — Police are on the lookout for a man they say sexually assaulted and robbed a 41-year-old Oak Park woman Monday on the Blue Line near Oak Park.

Area North detectives said in a news conference Tuesday night they hope by spreading the man's image, someone will recognize him and come forward to identify him to police.

A police alert released earlier Tuesday contains screen captures of the man's face from train security cameras and says the attack happened Monday around 3:10 p.m. after the woman boarded the Blue Line at Oak Park Avenue. The man who attacked her had boarded the same eastbound train two stops earlier at Forest Park.

Not long after the woman boarded the train, the man attacked her from behind, knocking her to the ground before sexually assaulting her and robbing her of an iPhone and cash. The train car was otherwise empty at the time of the incident, police said Tuesday night.

Detective Jackie Mok speaks during a news conference Tuesday night about a brutal sexual attack that took place Monday afternoon, in hopes someone will come forward with information. View Full Caption DNAinfo/Linze Rice

According to police, the man then exited the Blue Line train at Cicero Avenue, before switching directions and fleeing on a westbound train to Austin Boulevard. The woman was able to use the train's help button to call for assistance.

The woman suffered non life-threatening injuries and was being treated at a hospital, Detective Jackie Mok said during the news conference.

The man is described as black and wearing a blue and grey Columbia jacket, jeans and green-laced tennis shoes.

Police are asking anyone with information to call Area North Detectives at 312-744-8261. In the meantime, they are urging the public to remain alert, refrain from talking with strangers and to report any suspicious activity to police.

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