MELBOURNE, Australia (AP) — Michelle Payne, the first female jockey to win the Melbourne Cup, has been barred from racing and track work pending an inquiry into a positive doping test.

Racing Victoria, which governs thoroughbred racing in Australia’s Victoria state, said it would conduct an inquiry on Thursday into the results of Payne’s urine sample from the Swan Hill Cup on June 11.

Racing Victoria said stewards received a report from Racing Analytical Services Limited confirming the presence of Phentermine, an appetite suppressant and banned substance in accordance with Australian Rule of Racing 81B, in the sample provided.

The 31-year-old Payne rode and trained two horses on the nine-race program at Swan Hill, picking up a place on a four-year-old mare Sovereign Wealth.

Payne, who rode the 100-1 outsider Prince of Penzance to victory in Australia’s richest race in 2015, was stood down from riding last Friday.

She has recently returned to Australia following a trip to Britain, where she rode Kaspersky to fifth place in the Group 1 Queen Anne Stakes at Royal Ascot, and has requested to attend the inquiry in Melbourne.