WELLINGTON, Fla. — When Argentine veterinarian Felix Crespo injected 21 elite polo horses with a vitamin supplement shortly before a championship match in Florida, he never imagined they would all be dead the next day.

A week later, with the horses felled by a mysterious poison, the grief in Crespo's eyes speaks volumes. Deep pain lurks beneath the brim of his ball cap.

"I am not living," Crespo told The Associated Press on Saturday in his first interview since the horses died last Sunday. "I wouldn't wish this on my worst enemy."

Crespo stroked his mustache, his head slightly hung. His eyes drooped from a lack of sleep. He said he spends more time with the horses than his family.

"They are part of our family," said Crespo, a father of four.

At the Lechuza Caracas polo team's sprawling 60-acre ranch in South Florida's polo capital about 15 miles from the Atlantic Coast, Crespo was somber and soft-spoken. He sat with team manager Esteban Scott on a brown leather couch in a room decorated with horse pictures, just feet from the stables.

Both men are still in shock.

"For me, it's really a tragedy," said Crespo, who has spent his life around horses and breeds them in his home country. "It's going to be very tough to recover ... I don't know if I am going to be back to the same person."

A Florida pharmacy that prepared the supplement for the team on order from their local veterinarian said Thursday the strength of an ingredient was incorrect. The pharmacy would not say what the ingredient was or if the mix-up was in the prescription that came from the veterinarian.

Investigations into the horses' deaths continue, but an exact cause has not been pinpointed. Necropsies of the bodies discovered bleeding in their lungs.

Crespo, 53, has a license to practice in Argentina, but not in the U.S., so he serves as the team's training supervisor here.

He can administer shots, but can't prescribe medication. The team turned to a Florida veterinarian it has used for nine years to place the pharmacy order for the supplement given to the horses on that fateful day.

The prized ponies from the Venezuelan-owned team began collapsing last Sunday as they were unloaded from trailers at the International Polo Club Palm Beach, with some dying at the scene and others hours later.

They were set to compete in the sport's U.S. Open tournament and were seen as top contenders. Twelve of the dead horses belonged to prominent Venezuelan banker Victor Vargas, the team's owner. The rest were owned by players.

The match day began like any other — grooming, feeding, exercise, rest.

The 21 most elite of the 38 horses that were headed to the field were given the supplement that was supposed to be a mixture of vitamin B, potassium, magnesium and selenium to help the fatigued animals recover after the match.

But something went wrong. Two of the horses — 7-year-old Turca and 6-year-old Pelusa — fell ill with shakes, fever and sweats, Crespo said.

They were kept behind at the stables, while the 36 others were sent to the polo field.

"They were showing signs of some kind of allergic reaction that we didn't know what it was," said Scott, the team manager.

The horses arrived at the field and Scott, 39, got a frantic call. Something was wrong.

"What I find is that when they opened the gate of the trailer, one more mare had collapsed and died on the trip," he said. "Within a few minutes, three more horses started showing signs of dizziness, sweating and heavy breathing."

The sick horses were sent back to the barn. But it didn't stop there.

The horses began dropping beside the field.

People were "crying, hugging them," Scott said. "We didn't know what was wrong."

Then the unimaginable happened.

"The horses started passing away one by one," Scott said.

By the next day, all 21 horses that got the shots were dead.

The team, a tight-knit group of about 50 people that work together 11 months a year, is now mourning.

"You're very connected with the horses. You learn to care about them and love them," Scott said. "This is a day that is going to be in our minds for the rest of our lives."

The team heads to England in a month, where they stable about 50 horses, for another match.

"Those horses will never be replaced," Scott said. "But we're going to get over this ... We are a tough team."