LONDON, Jan 4 (AP/UNB) - Animal health experts are trying to determine the cause of a serious canine disease found at Queen Elizabeth II’s Sandringham Estate.

The disease, known as Seasonal Canine Illness, has not affected the queen’s beloved Corgi pets but it has sickened about 30 dogs walked by members of the public on open areas of the 20,000-acre (8,000-hectare) estate in rural Norfolk.

The Animal Health Trust said Tuesday that no conclusive answers have been found for the mysterious disease that begins with vomiting, diarrhea and a high fever.

Investigators say the disease has been found in other parts of England as well, with about 70 cases reported.

Signs are posted urging dog owners who take their pets to Sandringham Estate to keep them on leashes as a precaution.