Passengers walk along the tracks at the scene of a Blue Line train derailment. (Courtesy: Dan Hamilton)

Updated 04/11/14 – 8:38 a.m.

A CTA Blue Line train headed to Forest Park derailed slightly Thursday night, after hitting a truck tire that had fallen on the tracks.

The train was leaving the Cicero station in the South Austin neighborhood around 7:40 p.m. , when a set of wheels on one of the cars derailed after hitting a tire resting on the tracks.

Officials said the tire came from a semi-trailer truck lost a tire on the Eisenhower Expressway, which runs alongside the Blue Line tracks. The tire somehow bounced over the fence separating the expressway from the tracks, and landed on one of the rails.

Passengers who were riding the train at the time said it was a jolting experience.

“Suddenly there was a big jar. The train shook. It felt a little bit like it was derailing. The conductor stopped the train pretty quick,” Dan Hamilton said. “We’re all kind of looking around at each other, trying to figure out what happened.”

Some passengers couldn’t help but think about a much more serious derailment on the Blue Line last month, when a train jumped the tracks at O’Hare International Airport, and climbed an escalator.

“When you first hit whatever it is, and the train is jarring, and you’re feeling things you’ve never felt before, it’s a little scary, sure. You know, you’re thinking about conductors maybe falling asleep or whatever, but clearly that’s not what happened here,” Hamilton said. “Something was … on the tracks and we hit it.”

The operator in the O’Hare derailment has been fired, after admitting she fell asleep at the controls just before the crash, and once before in February.

Federal investigators also have said an automated braking system known as a “track trip” was too close to the end of the tracks to stop a train going approximately 25 mph. The CTA has since moved the track trip back and reduced the speed limit for trains entering the O’Hare station to 15 mph.

After Thursday night’s derailment, passengers were evacuated from the train, and were escorted alongside the tracks back to the Cicero station, where buses took them to the next stop.

No one was injured.

It took about two hours to get the train back on the tracks.

Blue Line trains shared a single track between the Pulaski and Austin stations for a while after the derailment, but service was back to normal in time for the morning rush.