Initially 14 students, ranging in age from 7 to 16, the bus driver and the driver of the escort vehicle were all taken to the hospital. The child is considered to be in critical condition. The driver was last seen heading east on Route 30, police said.
The sedan, with a male driver, continued traveling east.
Police said the driver who did not stop was in a light-colored, newer-model sedan that likely has front-bumper damage.
"There's a very good possibility that this vehicle, as it was traveling eastbound prior to the accident scene, may have been passing other vehicles", Bowman said.
Bowman said the eastbound vehicle tried to pass a tractor-trailer carrying an over-sized load and the rig's escort auto, also traveling east. It hit the escort auto and set off a "chain-reaction accident", Bowman said. One of the students suffering from a traumatic injury was airlifted to a local children's hospital. As the sedan driver was making the pass (into the opposing lane), the bus was approaching from that lane.More news: NY judge Garcia uninterested in FBI director job
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However, one student on the bus was attending the Locust Grove Campus for children in Pre-K through eighth grade and one was attending Lancaster Mennonite Middle School.
"Obviously, our first source is God and the strength that he provides in situations like this", said Lancaster Mennonite Superintendent Pam Tieszen.
"One student was ejected from the bus", reads a statement from the Lancaster County District Attorney's Office.
If you have any information that could help investigators, contact the East Lampeter police at 717-291-4676.
This story is developing. Check back with LancasterOnline for updates.