An unknown medical emergency forced a school bus driver to stop on Highway 525 in front of the Dairy Queen and Chevron gas station in Clinton on Thursday.

Emergency responders and a South Whidbey School District official said the nature of the emergency was unclear.

The bus was southbound on the state route and sideswiped a truck heading north. Neither the truck’s driver nor students were injured.

“They weren’t shook up at all,” said South Whidbey Fire/EMS Deputy Chief Jon Beck of the elementary school students, some of whom were peering out of the bus windows while waiting for another bus or their parents to pick them up.

The school bus driver was taken to Providence Hospital in Everett. His condition was not known Friday at press time.

When first responders arrived, they removed the driver from the school bus so as not to alarm students as they checked his vitals.

Two other incidents — a T-bone car crash in Bayview and a woman who fell from a horse in the Saratoga woods — had tied up South Whidbey’s ambulances, and one was called south from Oak Harbor, delaying the driver’s transport to the hospital.

“The driver wasn’t really quite alert,” Beck said.

Dan Poolman, assistant superintendent for business and transportation, said the bus driver did not have any other crashes or a known medical condition.

“He’s been driving buses longer than I have worked for the district,” Poolman said.

The school bus sustained little damage from the glancing blow with the truck, and Poolman guessed no repairs are needed. The truck, however, was damaged, including a flat rear driver-side tire. Repair costs are unknown.

A total of 18 students were on the bus, which serves Bob Galbreath Road, Glendale and the Deer Lake area. Some were picked up by their parents, while others were loaded onto a different bus and taken home.