No one suffered life-threatening injuries in the Blue Line derailment at O'Hare International Airport, Chicago Fire Commissioner Jose Santiago said during a morning briefing.
An enormous disaster was avoided thanks to the timing of the crash just before 3 a.m. The bustling station is usually packed with travelers using the major airport, but Chicago Transit Authority official said the crash happened at a traditionally quiet time.
Denise Adams, a passenger on the train, told the Chicago Sun-Times she heard a loud noise during the impact.
"I heard a 'Boom!' and when I got off the train, the train was all the way up the escalator," she said. "It was a lot of panic."
CTA investigators along with the city fire department and police were reviewing security footage and interviewing the driver and other CTA workers to pin down the cause of the accident. National Transportation Safety Board was leading the investigation.
"We will be looking at equipment. We will be looking at signals. We'll be looking at the human factor and any extenuating circumstances," CTA spokesman Brian Steele said. "But really at this point, it's far too soon to speculate."
Transit agency officials said crews were working to remove the train and fix the escalator, which received "significant damage." Hours after the crash, the front of the first car could still be seen near the top of the escalator.
Christopher Bushell, CTA's chief infrastructure officer, said it would likely be at least 12 to 24 hours before the station would reopen. He said workers will cut the train apart and remove it in pieces on a flatbed.
The CTA was busing passengers to and from O'Hare to the next station on the line.
The train appeared to have been going too fast as it approached the end-of-line station and didn't stop at a bumping post - a metal shock absorber at the end of the tracks.
"The train actually climbed over the last stop, jumped up on the sidewalk and then went up the stairs and escalator," Santiago said.
"Apparently (it) was traveling at a rate of speed that clearly was higher than a normal train would be," Steele said.
It wasn't clear how many people were on board at the time of the crash, but that it took place during what is "typically among our lowest ridership time," Steele said.
The injured were taken to area hospitals and Santiago said most were able to walk away from the wreck unaided.
Six of the injured, all of whom were in stable condition, were brought to Swedish Covenant Hospital in Chicago, said hospital spokesman Nick Przybyciel.
Evonne Woloshyn, a spokeswoman at Advocate Lutheran General Hospital in Park Ridge, said seven people were treated for minor "whiplash-type" injuries after complaining of head and neck pain. Most were released Monday morning and the rest were expected to be discharged later in the day.
In September, a CTA Blue Line train slammed into another train at a suburban Chicago station, injuring as many as four dozen commuters.