It sounds like something that could have come out of a novel by the famous veterinarian James Herriot, but, astoundingly, a dog has died having allegedly been poisoned at Crufts, the famous British dog show which took place this week.

And now the murder mystery is deepening with claims by a judge at the competition that two other dogs have been poisoned at the event.

The three-year-old Irish setter known as Jagger collapsed and died after returning home to Belgium on Friday.

Police in Belgium are investigating the killing. Investigations are understood to be focusing on two lines of inquiry, either that the dog was fed cubes of poison meat by a member of the public or that it was taken out by a jealous rival competitor.

It has been confirmed today that the dog was poisoned, and a full toxicology report is expected next week.

Jagger, who came second in his class at Birmingham's NEC on Thursday, is co-owned by Belgian Aleksandra Lauwers and British breeder Dee Milligan-Bott.

Nothing appeared untoward until dogs and owners had returned to Mrs Milligan-Bott’s home on Friday.

Mrs Milligan-Bott told industry website Dogworld, "All the dogs were all running and playing together and Jagger seemed a bit tired, unable to keep up with the others. Three or four hours later after getting back to Belgium he collapsed and by the time the vet arrived he was dead.

"The post-mortem showed that two or three different poisons were used and that it is likely it was administered on Thursday morning; we’re now waiting for exact toxicology reports. Whoever did this knew what they were doing, trying to get exactly the right type of poison with a slow release.

"They take this kind of thing far more seriously in Belgium and the police and Belgian SPCA searched Alex’s house and took blood from all the other dogs."

According to Dogworld, Mrs Milligan-Bott believes another of her dogs - a hound named Pot Noodle - was in fact the target of the dog-killer.

Mrs Milligan-Bott added, "There would have been windows of opportunity for someone to feed Jagger something at Crufts. It’s been suggested that someone’s really got it in for us, and to not let it get to us. There do seem to be too many coincidences. You go to shows trying to win, and one of our dogs is on a roll at the moment, and our kennel had a good day at Crufts on Thursday. We’re very proud of our record and maybe some people aren’t happy.

"But there’s no excuse for this. Sometimes you can’t prove anything but you know in your gut what has happened and that something very untoward is going on.”

The situation became even more worrying after a judge told the Telegraph that they believed two other dogs had been poisoned.

The judge, who spoke on the condition of anonymity, said: “I saw one of the prize-winning dogs being sick in the ring on Friday.

“The lady who owned the dog was very upset, he is a top winning dog. His eyes were rolling and she had to take him to the vet. She thought someone had poisoned him, although she had no proof.

“Then there was another lady with a champion bitch who was sick in the morning, then she was ok when she was shown, and when she got home she was passing blood. Both ladies thought their dogs had been poisoned.”

Mrs Lauwers's husband Willem said the couple were "devastated" by the death of Jagger."My wife has to go and give a statement to the police tomorrow and we'll see what happens," he told the BBC."We're quite successful and that can of course make people jealous," he said, "I can only hope it wasn't an act of jealousy by another competitor, but just a lunatic."TV presenter Clare Balding tweeted: "Everyone at #Crufts2015 horrified at death of Irish Setter Jagger."