Police on Saturday were attempting to determine why a tractor-trailer rig barreled into a Chicago Transit Authority train station, killing two people and injuring 21.
Their investigation included questioning the 51-year-old truck driver, who was briefly hospitalized after the accident during the Friday evening rush hour.
The driver, who authorities said tested negative for alcohol, was led away in handcuffs after he was released from a hospital Friday night. He had not been charged with any crime as of Saturday morning, said police spokeswoman Laura Kubiak. She declined to identify the driver.
The truck careened off a nearby expressway and veered into the busy Cermak-Chinatown Red Line train station and a bus shelter.
The truck ended up wedged inside a stairwell leading from the street-level station to the elevated train's platform above. Two women died at the scene, police said.
At least one surveillance video camera captured the crash, said CTA spokeswoman Noelle Gaffney.
"We've turned those images over to police," Gaffney said.
'Heard the big bang'
Twenty-one people were taken to hospitals, fire department spokesman Larry Langford said. Eleven were in critical condition, four of them children, Langford. It was not immediately clear Saturday how many patients remained in hospitals.
If it hadn't been for a delay leaving work, said Elliott Reed, a 30-year-old bank security officer, he could have been one of the victims. He said he "heard the big bang and saw the truck go right into the station."
Most of those injured were in the bus shelter or the train station stairwell, said fire department spokeswoman Eve Rodriguez.
The truck didn't appear to slow down before the impact, witnesses said.
Engineers determined there was no structural damage to the overhead platform, but the stairs had significant damage, said CTA President Ron Huberman.
The station, just south of downtown, reopened Saturday but travelers were told to use a nearby auxiliary entrance because the main entrance and the stairwell were closed, Gaffney said.
The truck was operated by Whiteline Express Ltd. of Plymouth, Mich., the company confirmed Saturday. A company spokeswoman declined to comment.