The Kennel Club, which runs the world-famous Crufts show, said the tests showed that the dog, known as Jagger, died on March 7 after returning to his home in Belgium of fast-acting poisons that usually would cause symptoms within three to four hours. That would rule out a poisoning at Crufts, which took place March 5.
"It is highly likely that the poisons, thought to be on a piece of beef, were eaten in Belgium, shortly before Jagger's death," the club said of the results.
The dog ingested aldicarb and carbofuran, two insecticides used in agriculture but not approved in the European Union, the club said.
The Kennel Club said no dogs were shown to be sick at the show and no complaints were made to the police.
The part-owner of Jagger, breeder Jeremy Bott, declined to comment on the results. The office of the vet in Belgium confirmed the results of the tests were in, but referred all comments to the dog's owners.
News of Jagger's death made international headlines when it was revealed last week. Though the co-owners in both Belgium and Britain underscored that they did not believe another competitor to be involved, the mystery of how the dog became ill led to speculation that there might have been some malicious intent.
Canine competitions have long been the subject of rumours about unscrupulous behaviour — including owners slipping drugs to rival dogs.
Crufts is a particularly prestigious show. Founded in 1891, it is Britain's most famous dog event, attracting more than 21,000 competitors from 43 countries this year.
The club asked for space to allow the owners to grieve and urged people to be aware how easily a dog might ingest poison.
Associated Press reporter Raf Casert in Brussels, Belgium contributed to this story.