07/13/2012 03:25 EDT | Updated 09/11/2012 05:12 EDT

3 horses dead after Chuckwagon crash in Calgary

Calgary Stampede officials have confirmed three horses are dead and one is injured following a chuckwagon crash during a Thursday night race.

In a video of the accident, Chad Harden's wagon takes a serious tumble in the backstretch of the Rangeland Derby's fourth heat, which brought down a number of his horses and an outrider — a cowboy who loads poles at the start and must finish the race with the chuckwagon.

Stampede spokesperson Doug Fraser said two horses had to be put down by veterinarians. Harden and the outrider are both doing fine.

"One of Harden’s outrider horses also collided with the wagon and sustained serious injuries," Fraser told reporters in a prepared statement. "The left lead horse, which was the horse that collapsed, experienced a fatal event the nature of which is undetermined at this time. The right lead horse and the outrider horse were humanely euthanized due to the severity of their injuries."

The horse on the right wheel sustained non-life threatening injuries and is receiving veterinary attention, according to officials. The injuries will require surgery but the horse will survive.

The left wheeler and the other outrider horse were not injured.

A tearful Harden, overcome with grief after the loss of his horses, spoke to reporters shortly after the animals were euthanized on the dirt track, calling them "part of our family."

"We love those horses," he said, his voice breaking with emotion. "The outriding horse is an 18-year-old horse, I've had him for 13 years. He's part of our family, he's supposed to be my kid's horse."

Speaking of his right lead horse, which helped Harden win the 2009 Calgary Stampede, he said the horse was irreplaceable.

"They're just like humans, they're our family," he said. "It's just devastating for our whole family. It's hard to take."

The Stampede introduced changes last year aimed at making chuckwagon races safer for both horses and competitors.

Vancouver Humane Society calls for ban

The move came after six horses died in 2010 — two of heart attacks.

All horses are now inspected by veterinarians when the animals arrive at the Stampede and before and after every race.

The rules also require that the horses be given a mandatory day of rest after every four days of racing.

In order to reduce crowding on the track and the chance of collisions, the number of outriders alongside each competing chuckwagon was decreased to two from four. Several of the riders had been seriously injured in previous years.

At last year's Calgary Stampede, safety officials fined Chuckwagon driver Cliff Cunningham $12,500 — the steepest fine ever levied on a driver at the event — following a race collision that led to the death of a horse. The initial fine was only $2,500, but the penalty was later raised when investigating officials reviewed footage of the accident and interviewed other drivers involved.

Animal welfare groups have continued to cry foul over the popular Stampede, in spite of recent efforts to appease such organizations. Animal rights activists have long charged that the rodeo amounts to sanctioned animal cruelty.

The Vancouver Humane Society has specifically targeted the chuckwagon races, expressing concern over the safety of the event and noting that more than 50 horses involved in the races have been killed in the past 29 years.