The Chicago Fire Department said the city's Transit Authority train smashed into snow-removal equipment just before 10.35am on Thursday near Howard CTA station, according to the Associated Press.
There were 31 commuters and seven CTA workers on the train when it hit the slower-moving snow-removal equipment. Of the 31, 23 — including four children — were taken to nearby hospitals. Three of the injured were listed in critical condition, though none are reportedly suffering life-threatening injuries, according to assistant deputy chief paramedic Keith Gray.
The other passengers on the train when it hit the equipment declined medical assistance, Mr Gray said.
Passenger, Shayla Smith, was on her way to work in Wilmette and had just boarded a Purple Line train at Howard Station when she heard the crash. She said that passengers on her train began screaming and that an older woman fell from her seat.
"I just heard like a horrible boom sound," she told the Chicago Sun-Times. "It was like a weird boom sound. It felt like we're gonna tip over and I was wondering what's going on? My body shivered."
Video captured by local news stations showed the end of the commuter train had been crushed inward.
Some of the passengers exiting the train following the accident were taken to a triage centre for examination. At least one person was reportedly bleeding heavily from the head.
At least 15 ambulances were called out to the scene to assist with victim transport.
CTA officials are still investigating the cause of the crash. The incident has disrupted service on the CTA's Red, Purple, and Yellow lines, according to the CTA.