(Getty Images)

Estimate, a 5-year-old bay filly racehorse owned by Queen Elizabeth, has tested positive for the prohibited substance morphine, the BBC is reporting. Buckingham Palace said that the positive test resulted from “a consumption of a contaminated feed product.”

“On Thursday July 17 the British Horseracing Authority announced that a number of post-race samples, obtained from recent race meetings, had been found to indicate the presence of morphine, which is a prohibited substance on race days. Five horses, under the care of various trainers, were affected,” John Warren, the queen’s bloodstock and racing adviser, said in a statement, per RacingPost.com. “I can confirm that one of those horses was Estimate, the five year-old filly trained by Sir Michael Stoute and owned by The Queen. Initial indications are that the positive test resulted from the consumption of a contaminated feed product.

Warren said the queen had been informed of the news but that there would be no further comment until the British Horseracing Authority announces its full findings.

Morphine is banned because “it numbs pain and could give one horse an edge over another,” HRA spokesman Owen Byrne said in 2013. “Since 2002, 45 racehorses in the UK and nine in Ireland have returned positive dope tests for morphine, which have been linked to feed from two manufacturers — Dodson and Horrell and Connolly’s Red Mills,” Horse and Hound’s Charlotte White reported. “There is no firm evidence of where the morphine has come from, but the British Equestrian Trade Association (BETA) and feed manufacturers believe it to be a residue from poppies grown for medical use tainting feed processed on the same premises,” White continued.

As a 3-year-old in 2012, Estimate won the Queen’s Vase race, followed by wins in the Sagaro Stakes and Ascot Gold Cup in 2013. Estimate’s win in the latter race was the first by a horse owned by the reigning monarch. The queen was named the 2013 racehorse owner of the year by the Racehorse Owners Association “in recognition of her first success in the Gold Cup at Royal Ascot and contribution to the sport over more than 60 years,” the Express reported.

This year, Estimate finished second at the Gold Cup despite a long layoff from racing because of muscular problems in her hind right leg.

Queen Elizabeth is an avid lover of horses and has owned a sizable number over the years. Her horses have won all but one of the five British Classic Races.

After spending the first 17 years of his Post career writing and editing, Matt and the printed paper had an amicable divorce in 2014. He's now blogging and editing for the Early Lead and the Post's other Web-based products.