It happened just before 3am.
The train continued past the end of the platform and onto the escalators that lead up to airport terminals.
- NBC Chicago (@nbcchicago) March 24, 2014
NBC Chicago spoke to a TSA agent who wished to remain anonymous.
"I thought it was just a hard stop at the train didn't even slow down when it was coming in," the agent said. "It was chaos. People were freaking out. Trying to figure out what happened. Trying to make sure everyone was okay."
The injuries are not thought to be serious.
We will continue to update as more information becomes available.