A head-on collision involving two commuter trains in Chicago on Monday morning has left at least 48 people injured. Blue Line services were suspended between Forest Park and Austin so that emergency responders could finish clearing the wreckage.

"There was a train that was stopped at the station. Another train came through and looked like it blew the signal, because I heard beeping," Martinez Butler, a locomotive engineer not employed with the Blue Line, told NBC Chicago. "I'm a locomotive engineer. I know the systems, I know the sounds. When you hear those beepings it's warning you that there is an obstruction in front of you and you need to stop."

The incident occurred at around 8:00 a.m. in the Harlem station by Forest Park. According to officials, an out-of-service train struck a westbound train while it was stopped at the station. According to Amalgamated Transit Union worker, Robert Kelly, the train was going between 20 and 25 mph before it collided with the second train.

Thankfully, injuries such as neck and back pain were considered minor after approximately 48 passengers were taken to nearby hospitals. An official investigation by Chicago Police has been launched into the cause of the accident after suspicions arose that the train was stolen.

"Forest Park police are treating this as a crime scene," Forest Park Mayor, Anthony T. Calderone, told ABC 7 News.