But two days after the horse was euthanized immediately following the race, they were still looking for clues.

Larry Bramlage, the on-call veterinarian at Churchill Downs and a surgeon at Rood & Riddle Equine Hospital in Lexington, Ky., said that after studying the tape of the final strides taken by Eight Belles, he saw a dramatic weight shift just before she went down.

"She began to favor her right front for three strides," Bramlage said in a telephone interview last night. "Then she shifts dramatically to her left front. That was the third stride. . . . You could interpret it as a tripping, but I think it was a purposeful shift."

Bramlage said he realized after talking to trainer Larry Jones that Eight Belles sometimes "cross-fired" while galloping, which could have caused a problem, but he could not see that on the tape.

When a horse cross-fires, it runs with one lead in the front leg and the opposite lead in the back leg.

"I'm not saying it can't happen with a cross-fire; I just didn't happen to see it," Bramlage said.

Bramlage also did not rule out the possibility that microfractures had occurred during the race, which could have escalated as she throttled down afterward. However, he said the dramatic weight shift alone could have been enough to cause her problems to worsen.

"Her coordination [after the race] is not going to be what it would be with a normal horse," Bramlage said. "Your muscles are fatigued and your coordination is poor. She's a big filly anyway."

In a telephone interview yesterday, owner Rick Porter said, "We're 99.9 percent sure that it was just one of these freak accidents." Porter, of Wilmington, mentioned the possibility that the filly could have tripped, saying that after talking to Jones, "he thinks her legs may have crossed and that's why they were both broken in the same place."

In an interview Sunday at Churchill Downs, Jones talked about how the filly's ears had been up after the wire, indicating that she was not in any stress. He also said that Eight Belles had a cross-firing issue, although he added, "Now, did that lead to her breaking them? Don't know. That I'll never know."

After the race, jockey Gabriel Saez, who did not work the horse in the morning, had said Eight Belles had started "galloping funny" after the wire.

"I'll guarantee I know what he means," Jones said on Sunday, describing how the filly often cross-fired.

"Any time you pick her head up and pull on her, when she's ready to switch leads, she'd go to cross-fire, and I know that's what he felt. I'll just have to show him the pictures whenever I get them or get the film slowed down. . . . She'd be on the left lead in the front, right lead behind. She used to do that in the morning for the rider."

It was an issue Jones had worked on himself, getting on the horse in the morning.

Porter, speaking extensively for the first time, said: "It's the lowest of all lows for everybody involved with the horse." Among the messages of support he received, Porter said he appreciated a call from artist Jamie Wyeth, who turned the phone over to his father, Andrew. The 90-year-old artist also expressed his sympathy. The horse had been named for a Wyeth family home in Maine.

Eight Belles, the first filly to run in the Derby since 1999, had run a big race, getting into prime stalking position early, ultimately finishing 43/4 lengths behind winner Big Brown but 31/2 lengths ahead of third-place Denis of Cork. Three fillies have won the Derby, the last Winning Colors in 1988. Eight Belles, who had been based at Delaware Park, joined Lady Navarre in 1906 as the only fillies to finish second.

"I think there's no question that she validated the fact that she belonged in the Kentucky Derby - she finished strong," Porter said.

Porter will remember Eight Belles going by the wire. His group began celebrating her strong race.

"Then I saw an ambulance going by," he said. "I looked all around for my colors and I couldn't find them. I knew we were in trouble then."

Chelokee's surgery. Bramlage said he operated yesterday on Chelokee, a Michael Matz-trained 4-year-old who dislocated his front right leg in a race Friday at Churchill Downs. Bramlage said Chelokee's fetlock joint was fused in the lower leg and some artificial ligaments were added to the back of his pastern.

"That all went really well," Bramlage said, reporting that Chelokee was eating hay after the surgery.