Two racehorses were euthanized and another was injured at the Del Mar Racetrack Sunday, days after the start of the fall 2019 Bing Crosby Season, the Del Mar Thoroughbred Club confirmed.

The horses, Ghost Street, a maiden 3-year-old gelding making his fourth start, and Prayer Warrior, were the first and second deaths of the season, which opened on Friday.

Ghost Street suffered "a catastrophic injury" to his left leg in Sunday’s third race and was later euthanized, DMTC officials said. Ghost Street was competing on the grass course, they added.

Prayer Warrior was euthanized Sunday after suffering a similar injury in the sixth race on the main track, according to the Del Mar Racetrack.

Both horses sustained inoperable fractures to their sesamoid bones which are about the size of walnuts and located in the ankle joints of horses, said Dana Stead, Association Veterinarian for Del Mar Thoroughbred Club.

"They have to sustain all the weight of the horse throughout the stride. So you're talking a horse traveling 30 to 35 mph, putting all that weight on -- at any given time -- potentially one leg," Stead said. "Those bones sometimes cannot sustain the forces that go along with it."

A full autopsy will be conducted to try and determine the exact cause of the injuries, DMTC said.

Ghost Street was winless in four career starts with earnings of $6,311 for trainer Patrick Gallagher. Prayer Warrior had three wins in eight career starts and earnings of $37,501 for trainer Jeffrey Metz.

With heavy hearts, we can confirm that Prayer Warrior was humanely euthanized following an injury in today’s sixth race on the main track.



Our deepest sympathies to the Metz family and their team. — Del Mar Racetrack (@DelMarRacing) November 11, 2019

A third horse, Princess Dorian, suffered an injury to her left front leg in Sunday’s second race on the main track and was transported to a San Luis Rey Equine hospital for further care, Del Mar Racetrack tweeted.

The racetrack said she had X-rays and her prognosis was "improving."

Princess Dorian will be evaluated by an orthopedic surgeon. Surgery is the mostly likely option for the horse, according to Stead.

The mare is owned by Colorado Avalanche defenseman Erik Johnson, who tweeted, "She is worth nothing as a broodmare. If I can give her a great life I will do so any way possible." He included the hashtag HorsesComeFirst.

"We're all deeply saddened by the events today. It's definitely an anomaly. We've been the safest track since 2018," Stead added.

For the summer racing season, the Del Mar Racetrack introduced a new set of procedures to look at each horse and ensure they are fit to race, officials said. Two full-time veterinarians watch the horses train each morning, and observe how the animals are moving.

"Del Mar has implemented a series of industry-leading safety and welfare reforms over the past several years. We will continue our commitment to safety at the highest levels for our horses and riders," the racetrack said.

Two horses were killed at the Del Mar Racetrack after a head-on collision. NBC 7's Allison Ash has more.

Del Mar was the safest major track in the U.S. last year, according to the Jockey Club Equine Injury Database.

Despite the changes four horses died in training accidents during the track's summer racing season, which ended on Sept. 2nd.

On Aug. 12, a three-year-old filly named Bri Bri was euthanized after suffering a serious injury to her pelvis.

On July 30, a 3-year-old filly Bowl of Soul, trained by Bob Baffert and owned by Spendthrift Farm, was put down after a training injury to her back right fetlock, similar to a human ankle.

On the second day of the summer season, two horses died following a head-on collision during training. One of the horses made a sudden U-turn and collided with another galloping in its direction.

Both horses suffered cervical fractures and died on the racetrack. They were not euthanized, according to DMTC officials.

The track’s fall horse racing season returns for the next four weekends, complete with concerts and other cool events. NBC 7's Audra Stafford has more.

Animal advocates argue that horse safety will not be fully realized until racing is banned altogether.

"If you have a horse race, horses die. It's a given. Horses are never safe at the race track. Ever," Ellen Ericksen said.

PETA released a statement Sunday calling for a criminal investigation into the horse deaths.

"PETA has repeatedly asked that all racing be suspended until new regulations and measures to stop the carnage can be put into place."

"It's a balance trying to make everyone happy, do the best thing for the horse, that's what we're striving for," veterinarian Stead told NBC 7.

"I hope for patience from all the industry partners on both sides of the fence," Stead said. "We're going to be able to show that the protocols we're implementing are effective and they will continue to be more effective over time as they're further scrutinized."

Santa Anita has had 37 deaths since last December, including seven at its recently concluded fall meet. The highest profile was Mongolian Groom, who was euthanized after injuring his leg in the $6 million Breeders' Cup Classic shown on national television.