Alaska State Troopers say a bus crashed along the Sterling Highway Sunday morning after its driver apparently died of natural causes, sending at least seven people on board to a Soldotna hospital.

In an AST dispatch Sunday night, troopers say Sterling man Steven A. Battershall, 59, was at the wheel of the bus when it wrecked.

"Battershall was driving the bus northbound on the Sterling Highway near mile 90 when (he) went unconscious," troopers wrote. "The bus left the roadway and came to rest in a field."

According to Brad Nelson with Central Emergency Services, the bus was transporting 20 employees of Snug Harbor to Anchorage when it struck a tree.

Seven people were transported by CES to a nearby hospital for non-life threatening injuries.

Battershall's next of kin have been notified, and his body was sent to the state medical examiner's office for an autopsy.

Channel 2's Chris Klint contributed information to this story.