The crash involved several families on their way to the Six Flags Great America amusement park in Gurnee.
Dr. Bruce Hyman told ABC7 that 16 people were brought to Advocate Condell Medical Center in Libertyville, and three children were admitted in critical condition.
Some other children involved in the accident have already been released from the hospital.
"It was the first one that I was ever in, I didn't hear much, I just heard the airbags come in and then the back of the car that was flipped over hit us," Alina Lara, 9, car accident victim.
"There was a big semi-truck, it hit the car behind us, and then the car behind us hit the car," said Jacob Watkins, 6, car accident victim.
One child remains in Libertyville, and the other two critically-injured children were airlifted to Advocate Lutheran General Hospital, Dr. Hyman said.