“The Queen is absolutely devastated. The puppies were brought in to cheer her up during a very difficult period," the source told the publication.
“Everyone concerned is upset as this comes so soon after she lost her husband."
The puppy was a Dachshund and a Welsh Corgi mix, and was one of two dogs given to Her Majesty to cheer her up after Prince Philip fell ill.
The Queen named the dog Fergus after her maternal uncle Fergus Bowes-Lyon, who died in France during World War I. The second pup, Muick, is named after Loch Muick, a lake on the Balmoral Estate in Scotland, and was a corgi.
Her love for corgis started when she was a teenager, ever since her 18th birthday when she was given Susan, a corgi, as a gift.
Her Majesty bred Pembroke Welsh corgis ever since, and has owned more than thirty in her lifetime.
The sad news comes after it was revealed that the Queen will reportedly head to her favourite residence, Balmoral Castle, to grieve her husband's death.
The estate is the famed location of the royal couple’s honeymoon and the destination for many of their summer getaways.