However, The Kennel Club, which runs the Crufts competition, said the cause of Jagger's death has not been established.
"The facts surrounding Jagger’s sad death are still being established and we must stress that any other unsubstantiated rumours about dogs being poisoned are just that at this point," The Kennel Club said in a statement. "There are any number of reasons why a dog may display symptoms such as sickness and should a dog fall sick there are vets at the show who will examine the dog in question and file a report. We can confirm that no vets have raised concerns about poisoning and there have been no official complaints from any owners at Crufts 2015. We are aware that there are reports in the press regarding a number of breeds."
In addition, the West Midlands Police in England said in a prepared statement that "the force has not been approached by police in Belgium or the dog owner."
"If, following toxicology results in Belgium, the force is formally asked to conduct inquiries into the circumstances surrounding the death of the animal, an investigation will take place by officers in conjunction with Crufts and the NEC," the statement added.
Regardless of the circumstances, the news of Jagger’s death has rocked dog owners at Crufts, which is equivalent to Westminster in the U.S.
"The Kennel Club is deeply shocked and saddened to hear that Jagger the Irish setter died some 26 hours after leaving Crufts," said Caroline Kisko, the Kennel Club’s secretary.
So far, there have been no leads as to who was responsible for the prized pup’s death.
Jagger’s co-owners, Dee Milligan Bott and Jeremy Bott, read a short statement outside their home, saying they don’t think their dog was killed by another exhibitor at Crufts.
"We can't and we won't think this was an act of another exhibitor," the statement read. "If we thought this, we couldn't go on."
Nevertheless, speaking with the BBC, the breeder’s daughter, Amy Nettleton, said the family believes its beloved dog was deliberately killed, adding, "the autopsy showed very clearly there were cubes of meat in his tummy that were laced with poison."
Nettleton told the BBC it certainly wasn’t a dog lover who killed Jagger, noting that many people have access to the dogs at the competition.
"The general public can wander in and out of benches and can approach any dog that they feel fit, so to keep an eye on everybody that came up and spoke to any of the dogs is very difficult," she said. "We just wanted to raise awareness to find the perpetrators that did this to ensure that these kind of acts don’t happen again."