The Chicago Fire Department said most of the injuries were minor, however one person is listed in serious condition. The extent of his or her injuries is not known, but they are not considered life-threatening. Officials said a pregnant woman was also hurt.
Officials say two trains -- Amtrak train No. 391 to Carbondale and Metra Burlington Northern train No. 1242 -- were involved in a slow-speed collision around 8:15 a.m. One car had structural damage.
ABC7's planning editor Len Prazak was on the Metra train. He said, "There was a loud bang and we pushed forward, and a second or two later, there was a second loud bang... a conductor came rushing through asking if everybody was OK. Everybody in our car was OK. Then I heard him on his radio the call for ambulance and doctors."
The Amtrak train was empty, according to officials, and leaving Union Station as the Metra train, carrying between 1,000 and 1,500 passengers, arrived. The trains struck, but an exact cause has not been released. Metra officials said there may have been a switching error.
"Cars came in. We were just about there and it happened really far inside," said one passenger.
"Everyone was looking around trying to figure out what was going on but we realized we were going off the track. We thought it was a terrorist track," said a second.
"I was asleep, jostled awake," said a third. "Nobody was really hurt."
Passengers were evacuated onto Taylor Street and 10 buses were sent to pick them up and take them on to Union Station.
The incident briefly disrupted Union Station during the morning commute. Trains were able to move in and out of the hub again around 10 a.m. However, Metra is urging passengers to check for delays and platform information during the afternoon commute.
Officials later said that none of the cars came off the track.