Chatham, Illinois - At least four people, including children, were killed after a car crashed into a school building in Illinois on Monday.

Illinois State Police said the accident happened at an after school program in Chatham.

A vehicle drove into the east side of a YNOT After School Camp, plowing into people as it entered the building and crashed out the other side.

Police said those killed were believed to be between the ages of 4 and 18. Several others were injured and taken to hospital.

Accidents Former NCAA Woman of the Year and family members killed in upstate New York plane crash

The driver, who was alone in the car, was uninjured and transported to a hospital for evaluation, police added. ​ ​

Illinois Governor JB Pritzker said he was horrified and deeply saddened by the accident.

"Our community lost a group of bright and innocent young people with their whole lives ahead of them," he wrote on X.

"Parents said goodbye to their kids this morning not knowing it would be the last time. My heart is heavy for these families and the unimaginable grief they're experiencing - something that no parent should ever have to endure."

Classes in the Ball-Chatham School District will be held online on Tuesday in the wake of the tragedy.