“This decision was taken in the best interests of the animal and its welfare.”Russia’s UN envoy, Vassily Nebenzia, on Thursday asked at a Security Council meeting about Mr Skripal’s two cats and two guinea pigs. “What happened to these animals? Why doesn’t anyone mention them? Their condition is also an important piece of evidence,” he said.No information has been given about the second cat. The property was a focus of police activity in the aftermath of the attack, with other sites in the Wiltshire city combed over for clues.A government spokeswoman said: “The property in Wiltshire was sealed as part of the police investigation.”When a vet was able to access the property, two guinea pigs had sadly died. A cat was also found in a distressed state and a decision was taken by a veterinary surgeon to euthanise the animal to alleviate its suffering. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Two guinea pigs were found dead at the home of poisoned spy Sergei Skripal after the property was sealed off for investigations.The Department for Environment, Food and Rural Affairs added a cat was also found in a distressed state at the house and a decision was taken to euthanise the pet.Tensions between Russia and the United Kingdom have been high since Mr Skripal and his daughter Yulia were found unconscious on a park bench in Salisbury last month.Scotland Yard said Mr Skripal and his daughter first came into contact with the nerve agent at his home after detailed forensic testing showed the highest concentration of the substance was found on the front door.