Rory McIlroy has revealed the details of a bizarre incident that led to a spectator being ejected from the Wells Fargo Championship during Thursday's first round.

Defending champion McIlroy had just teed off on the par-three sixth hole at Quail Hollow, his 15th, when a golf ball was thrown onto the tee box - with an earplug stuck to it.

McIlroy, who came close to a hole-in-one and holed from four feet for birdie in his opening 73, told reporters: "It was sort of weird. That's never really happened to me before."

The world number three's playing partner Rickie Fowler was preparing to hit his tee shot when the ball landed, but laughed off the incident after carding a one-under-par 71.

"So random," Fowler said. "The guy tried to say it was a gift. I don't know why you would give a gift of a golf ball with an earplug attached to it."

McIlroy pointed out the spectator to security officials and he was removed from the course.