The Kennel Club says it has received no information about claims a second show dog may now have died after falling ill following Crufts.
The club, which organises the world famous show at Birmingham's NEC, said it "has received no details" after reports emerged today that a shih tzu had also died.
Neither was any shih tzu treated by the official Crufts vet during the four-day show last week, it added.
It comes after owners of an Irish setter known as Jagger claimed their dog had died after showing at Crufts on Thursday, having apparently been fed poisoned chunks of steak.
A toxicologist report on that dog, whose show name was Thendara Satisfaction, is expected next week according to its co-owner Aleksandra Lauwers.
In a statement, a Crufts spokeswoman said: "The Kennel Club has received no details about the shih tzu who has allegedly died and whose identity remains unknown and we can confirm that no shih tzus were seen by the show vet at Crufts.
"We cannot look into claims about which we have no direct information, which is why it essential that people come forward with any concerns."
The Kennel Club had earlier said it was aware of reports several other dogs - including a shih tzu - together with a West Highland white terrier and an Afghan hound had also fallen ill after this year's show following claims made by other owners in the Daily Telegraph.
Meanwhile, Ms Lauwers, who lives in Belgium, today said toxicological tests were being carried out on samples from Jagger at the Faculty of Veterinary Medicine at Ghent University.
Ms Lauwers, writing on her Facebook page, said: "Samples are at the moment under investigation and result will be known not earlier than in a week time.
"(The) Result will be released only to owners and vet clinic and only then (a) public statement will be done."
Jagger's joint owners Ms Lauwers and Dee Milligan-Bott, of Kilby near Wigston in Leicestershire, claim steak laced with unknown poisons was found after an autopsy by a Belgian vet.
A spokeswoman for the Kennel Club said: "The facts surrounding Jagger's sad death are still being established. With regards to speculation about any other incidents involving other dogs, we must stress that these are at this stage just rumours.
"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 Crufts who will examine the dog in question and file a report."
She added: "As with any international competition, rumours of sabotage do occasionally surface. This of course is not in the spirit of competition and will not be tolerated.
"Anyone caught attempting to deliberately sabotage another competitor's performance, particularly if a dog's welfare is put at risk, will face severe disciplinary action, which could include a ban on competing at all Kennel Club-licensed events.
"Furthermore, anyone who puts a dog's welfare at risk could face prosecution under the Animal Welfare Act."
No vets have raised concerns about poisoning and there have been no official complaints from any other owners at Crufts, she added.
Mrs Milligan-Bott called Jagger's death "a heinous crime" but believes the attack was random rather than targeted.
Speaking yesterday alongside husband Jeremy Bott outside their home, the couple said they were grieving but vowed to return to the show next year.
Mr Bott said: "This one isolated incident will not spoil our enjoyment to show and compete with our lovely dogs."
Jagger had come second in his class during competition on Thursday.
West Midlands Police said they have not received a complaint or been asked to investigate but they are liaising with Crufts officials and the NEC to secure potential evidence.
The Kennel Club asked anybody who has any information about alleged poisoning at Crufts to email firstname.lastname@example.org.
Asked by reporters for his thoughts on the mystery earlier, Prime Minister David Cameron said, if true, it was "an unbelievably awful thing to do" to an animal and his "heart goes out" to Jagger's owners.
Speaking to Heart North West radio, he said: "As a dog and cat lover myself, your heart goes out to a family that sees that happen.
"I remember listening to the owner on the radio talking about the toxicology report and how they had found lumps of meat that had poison in. You think 'Who would go to such a length, who would do that? What an unbelievably awful thing to do'."
Asked if he was stepping up security for Downing Street cat Larry in the wake of the poisoning, the Prime Minister added: "As for Larry, he doesn't get up and get out much, so I think he's probably pretty safe sitting on the chair in the hallway, watching the world go by.
"But I'll double the security around him and make sure he's OK."
This year's Best in Show crown was secured by Scottish terrier Knopa.