A Chicago commuter train collided with rail equipment Thursday morning, injuring more than 20 people, some of them critically, fire officials said.

The Chicago Fire Department said the Chicago Transit Authority train crashed into snow-removal equipment just before 10:35 a.m. on the city’s North Side near the Howard CTA station.

The Yellow Line train carrying 31 commuters and seven CTA workers was southbound from Skokie when it collided with the slower-moving rail equipment, said Robert Jurewicz, the Chicago Fire Department’s second district chief.

Twenty-three people, including four children, were taken to area hospitals and about three of those injured were in critical condition, although no one suffered life-threatening injuries, said Keith Gray, assistant deputy chief paramedic.

He said the 15 others who were on the train declined medical treatment at the scene.

Shayla Smith, who was headed to work in Wilmette, had just boarded a Purple Line train at Howard when she heard the collision. She said passengers on her train began screaming, and she saw an elderly woman nearly fall out of 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.”

Television video showed one end of the train crushed and pushed in.

As passengers were led off the train, some were brought into a triage center lined with stretchers to be assessed, with at least one seen bleeding heavily from the head.

At least 15 ambulances were dispatched to the scene.

CTA officials said the cause of the crash remains under investigation. Train service on CTA’s Red, Purple and Yellow lines had been temporarily suspended due to the crash, the commuter service said on its website.