Queen Elizabeth's Royal Ascot Racehorse Fails Dope Test
07/23/2014 AT 12:05 PM EDT
The British Horseracing Authority announced last week that tests on five horses under the care of various trainers showed the presence of morphine in their "A" samples.
On Tuesday, the queen's bloodstock and racing adviser, John Warren, said that the monarch's 5-year-old filly Estimate was one of the five.
Buckingham Palace said that early indications suggest that Estimate consumed the substance as a result of contaminated feed.
Warren said in a statement that Estimate's trainer Michael Stoute "is working closely with the feed company involved to discover how the product may have become contaminated prior to delivery to his stables."
Estimate finished second in this year's Gold Cup behind Leading Light.
Warren added, "Her Majesty has been informed of the situation."
Previously, Britain's most publicized case of a horse testing positive for morphine was Be My Royal after he had won the 2002 Hennessy Gold Cup at Newbury. The horse was subsequently disqualified.