Thirty-two people were injured after a Chicago Transit Authority train derailed and hit a platform at O'Hare International Airport early on Monday, with its front car landing on an escalator and stairs, a city fire official said.
It was not immediately clear how fast the train was moving, but authorities were looking at speed as a possible factor, said transit authority spokesman Brian Steele.
"It's evident the train was going faster than it should," he said at the scene.
The female train operator was among those hurt, though neither she nor any of the passengers faced life-threatening injuries, said Chicago Fire Department spokesman Larry Langford.
"Fortunately nobody was on the staircase," he said. "Anybody on the staircase probably would have been killed."
Langford said the eight-car train jumped a bumper at the end of the line just before 3:00 a.m. Chicago time.
The National Transportation Safety Board is investigating the cause of the derailment, said transit authority spokeswoman Tammy Chase. She said train service on part of the line may be suspended for up to 24 hours. Bus shuttles were available.
The injured passengers, in conditions ranging from fair to serious, were taken to four local hospitals with mostly bumps and bruises, officials said.
Passersby gawked at the crash scene, with some people saying the incident made them a little more nervous about traveling by train.
"I feel like there's accidents all the time with the trains, but not this bad," said Meghan Cassin, 25, a Chicago resident who was heading to work after a trip to Florida. "They take corners really fast."In September, a Chicago Transit Authority train collided with a standing train at a station in a western suburb of Chicago during the morning rush hour, leaving at least 33 people injured.