Hall of Fame jockey Victor Espinoza has suffered a fractured vertebra in a fall during trackwork at Del Mar.

Racetrack officials say Bobby Abu Dhabi suffered an apparent fatal heart attack during a work-out.

Espinoza was thrown off the horse and lay motionless for several minutes before being fitted with a neck brace and taken by ambulance to a hospital.

HIs agent Brian Beach says the 46-year-old suffered a fractured C3 vertebra in his neck and a "stinger" to the left shoulder and arm.

He said Espinoza, who guided American Pharoah to the Triple Crown in 2015, suffered no paralysis or other broken bones and was expected to make a full recovery.

"It looks like we dodged a bullet," Beach said.