PHILADELPHIA — State officials are investigating whether a veterinarian used a gun to euthanize a racehorse at a track near Philadelphia, a possible violation of track rules and racing industry standards.

Racehorses are typically put down with an overdose of barbiturates, and guns are often prohibited on and around tracks, experts said.

The reported gunshot death at Philadelphia Park is being reviewed by the Pennsylvania Racing Commission, track stewards and local police, commission spokesman Chris Ryder told The Associated Press on Friday.

The probe involves Dr. Thomas J. Lurito, a track veterinarian, he said. Lurito did not immediately return messages left at several listed numbers.

"My understanding was it was an attempt to euthanize the horse," Ryder said.

Philadelphia Park prohibits weapons unless someone is permitted by the racing commission to carry one, he said.

Gunshots can be a humane way to put down animals, but the practice is no longer seen at U.S. racetracks, experts said.

"Frankly, I'm a little taken aback. It's just not the way it's done," said veterinarian Rick Arthur, the equine medical director to the California Horse Racing Board.

Ryder could not immediately provide the date of the death, the reason the horse was being put down or other details. Messages left with Philadelphia Park and police in Bensalem were not immediately returned.

The death was first reported by racing industry publications, which said the horse was a 4-year-old filly.