Mornington trainers Mark Riley and Kane Harris have both had horses return positive swabs to the same prohibited substance.

The Riley-trained Undercover Poet was found to have the short-acting corticosteroid Dexamethasone in his system in a sample taken after he won a maiden at Mornington on New Year's Day.

A swab taken from the Harris-trained Crooner before he was unplaced at Flemington on the same day also contained Dexamethasone.

The trainers were told of the initial findings last month with analysis of the B samples confirming the results.