The driver of a vehicle involved in a fatal crash at an after-school camp in Chatham, Illinois, earlier this week was not under the influence of alcohol or drugs, Illinois State Police officials said Thursday.

At 3:20 p.m. Monday, a car drove through Youth Need Other Things Outdoors, killing four and injuring six others.

Police said the driver, a 44-year-old Chatham woman, was uninjured and transported to a hospital for evaluation. She has not been charged.

Investigators continue to look into the cause or motive of the crash, State Police Director Brendan Kelly said during a news briefing Thursday to provide an update on the investigation.

“There’s just no evidence that would indicate that this was something that was intended as some type of mass violence or terrorist attack,” Kelly said.

There is some evidence indicating the possibility of a medical emergency leading up to the crash, Kelly said, “However, the investigation of this information and other evidence has not yet concluded.”

Four girls, Alma Buhnerkempe, 7, Kathryn Corley, 7, Ainsley Johnson, 8 of Chatham, and Rylee Britton, 18 of Springfield, were pronounced dead at the scene. Two of the six people who were injured have been released from an area hospital. In the days following the crash, hundreds of people gathered for vigils in Chatham, a town of less than 15,000 people, about 12 miles from Springfield. Any decision to press charges will be made by prosecutors, Kelly said.

“Our people and all first responders are tough, but when a child dies, when children die, it weighs on their hearts and their minds and their souls,” Kelly said. “We offer our sincere and heartfelt condolences to the family, friends and Chatham community during this difficult time.”

The incident has drawn national attention, and elected officials have offered their condolences.

“I am horrified and deeply saddened by the deaths of children and numerous injuries in Chatham this afternoon,” Illinois Gov. JB Pritzker said in a statement Monday. “My heart is heavy for these families and the unimaginable grief they’re experiencing — something that no parent should ever have to endure.”