A Chicago Transit Authority Blue Line train derailed early on Monday morning at O’Hare International Airport.
The eight-car train continued through the platform and rose up an escalator at about 3 a.m. local time.
Chicago Fire Department Commissioner Jose Santiago said 32 people were taken to hospital, although none of the injuries were thought to be life-threatening.
CTA spokesman Brian Steele also told reporters that the train appeared to be traveling faster than usual when entering the station.
"We will be looking at everything — equipment, signals, the human factor," he added.