Still, 14 people were sent to hospitals, and it was a scary situation for the dozens of riders on board the train.
The train derailed at approximately 12 p.m. Saturday near 59th Street and Prairie. That's where the Green Line splits into two separate branches.
A similar derailment occurred at the same spot last year.
Saturday, firefighters helped scared passengers off the derailed train just moments after one of its cars left the track.
"It was frightening, very," said passenger Joanne Pratt.
The accident happened as a downtown-bound train motored toward its next stop at the Garfield station. Passengers say the train had stopped at the junction while another passed going in the opposite direction.
"She went, she went, she went, then she stopped. Then, she went back, and all of a sudden, the last car went off the tracks. So, we started hollering, 'Stop! Stop! Stop!' By the grace of God she stopped, and we're still here," said Kevin Lee, also a passenger.
Riders say it was as the operator approached the junction turn near 59th and Prairie that something went wrong.
"She was going forward. Then, we stopped for a minute, and then started backing up. Another CTA lady was on the trains and she said to stop because the train was going off the tracks, and everyone started hollering," said passenger Prentice Gibson.
"The evacuations went smoothly for us. We had a staircase," said Chief Patrick Malone of the Chicago Fire Dept.
Fortunately, no one was seriously injured in the incident, which brought 50 firefighters and 10 ambulances.
But while some people waited for help, others simply panicked, jumping onto the roof of a nearby CTA maintenance building.
"I pulled the thing and jumped off. That was just my first instinct. It wasn't fear or anything. I've got to stay alive," passenger Kelvin Gregory said.
"I was scared. I jumped after another guy jumped. He opened the door, and we jumped off," Leshae Lyles said.
Transit officials said they were still investigating the accident Saturday evening.
"We're still in the process of investigation. So, before we speculate, we'd rather have an opportunity to talk to the operator and hear what they have to say," CTA spokesperson Noelle Gaffney said.
Because a similar kind of derailment occurred in May 2008 when a southbound train left the tracks near the turn, 20th Ward Ald. Willie Cochran was asking questions Saturday.
"There we're some slight repairs, and we're very concerned about the conditions of these tracks at this point," Cochran said.
In the 2008 derailment incident, two of a train's four cars jumped the tracks. Fourteen people were injured in that incident and taken to hospitals. None of the injuries were serious, but the fire department had to remove several people from the train with rescue apparatus.
The CTA quickly determined that operator error led to last year's train derailment. The agency said said the operator ignored a stop signal and overrode a braking mechanism.
Per policy, the train operator in Saturday's derailment will submit to drug and alcohol testing.
There was no update Saturday night from the CTA on whether the operator or signal recorders had given them information that may pinpoint the cause of the derailment.