The bus was last inspected four days before the crash. It passed the inspection, according to records from the Indiana State Police.
Sgt. Kendale Adams from the Indianapolis Metropolitan Police Department also said they are considering operator error as a cause, but it hasn't been fully determined as the cause.
"We just believe this was a tragic operator error that resulted in the death of a beloved community member," Sgt. Adams said. "It's very unfortunate and it's really too early to determine exactly what happened."
Police say the bus driver showed no signs of impairment, and voluntarily consented to a blood draw.
To officially rule out drugs or alcohol as a factor, authorities must wait for toxicology results, which could take weeks.
There was also surveillance video from the bus and the school. Police are using them in the investigation, but won't be releasing it to the public due to their graphic nature.