The world's biggest dog show was thrust into a murder mystery fit for an Agatha Christie novel when a champion Irish setter died after its owner said it had been fed steak laced with poison.

The death of three-year-old Jagger rocked Britain's Crufts show, held annually since the reign of Queen Victoria, and unnerved a dog-showing world that some fear may have just become too competitive.

"An autopsy has revealed he was poisoned," Dee Milligan-Bott, an experienced Irish setter kennel owner who has officiated at Crufts, said of her dog, whose pedigree name is Thendara Satisfaction.

Milligan-Bott said the autopsy showed Jagger had been fed steak laced with several types of poison that led to a painful death for the dog on its return to Belgium.

"The timings from the autopsy make it clear the only place this could have been given to Jagger was while on his bench at Crufts," added Milligan-Bott, who said the police had been informed.

However, police in her home town of Tongeren in the east of Belgium, said they had not received a complaint.

Kennel owners flock to a cavernous conference centre outside Birmingham for Crufts, preparing their pedigree dogs for judgement against 21,500 others in a series of competitions that culminate in Best in Show.

A Scottish terrier from Russia won that title on Sunday, two days after Jagger's death.

The show was founded by Charles Cruft, who worked for a dog biscuit manufacturer. Winners, which emerge from categories such as toy dogs, gun dogs, hounds and terriers, often have striking names. A poodle called Afterglow Maverick Sabre, also known as Ricky, won Best in Show last year.

The Kennel Club, which organises Crufts, issued a statement of condolence.

"The Kennel Club is deeply shocked and saddened to hear that Jagger the Irish Setter died some 26 hours after leaving Crufts," Kennel Club Secretary Caroline Kisko said.

"We have spoken to his owners and our heartfelt sympathies go out to them. We understand that the toxicology report is due next week and until that time we cannot know the cause of this tragic incident," Kisko said.

A Kennel Club spokeswoman said it was unclear where the alleged incident happened and that until the toxicology report was received it was difficult to speculate.

Despite that, some British newspapers suggested that another similar-looking setter, called Pot Noodle, may have been the intended victim.

In any case, the tabloid Sun reported, "police are following all leads".