Story highlights Three-year-old Irish setter Jagger died suddenly after competing at Crufts dog show

An autopsy revealed poison sewn into cubes of beef in his stomach

"We can't fathom why anyone would do this," owner-breeder Dee Milligan-Bott tells CNN

London (CNN) An investigation is underway after a canine competitor died the day after taking part in Crufts, one of the world's most prestigious dog shows. An autopsy indicates he was poisoned.

Three-year-old Irish setter Thendara Satisfaction -- known to his owners as Jagger -- took second prize in his class at the event in Birmingham, central England, on Thursday.

But just a day later, after returning home to Belgium, he became ill. Owner-breeder Dee Milligan-Bott told CNN Jagger was "finding it hard to breathe" so a veterinarian was called, but the dog died before he could get there.

"The vet thought it was suspicious, so carried out an autopsy," she said. "They found cubes of beef in his stomach that had at least two types of poison inside. Pieces of beef had been stitched together so that the poison didn't come out.

"He had enough in his system to kill a horse, according to the vet," said Milligan-Bott, who is at a loss to explain why Jagger was targeted: "We can't fathom why anyone would do this."

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