A Chicago transit spokeswoman says a train derailment was probably caused by operator error.
Fourteen people were hospitalized after the elevated train left the tracks Wednesday.
Agency spokeswoman Noelle Gaffney says an operator apparently failed to heed a stop signal. The train automatically stopped when it activated a trip.
But she says the operator moved the train forward again before the tracks could be switched into the proper position.
Gaffney says there is still a possibility the aging transit system played a role.