Aidan O'Brien was referred to the British Horseracing Authority after reportedly refusing to allow raceday officials to examine Cape Blanco following his win in the totesport Dante Stakes at York.
The Ballydoyle trainer watched from County Tipperary as Cape Blanco galloped to second-favouritism for the Investec Derby, after which rumours circulated about his well-being.
Television pictures appeared to show the colt being lame and stiff, but representatives from Ballydoyle and Coolmore insisted the horse was fine.
In an attempt to settle the matter, stipendiary steward, Robert Earnshaw, and BHA vet, Lynn Hillyer, both spoke to O'Brien by phone but he was said to have refused for the winner to be examined and declined an invitation for his travelling head lad, Pat Keating, to meet with the stewards.
Earnshaw said: 'Our vet is down at the stables but Mr O'Brien has refused to have the horses trotted up in front of the vet.
'The lad has loaded the horse up and is heading for the airport.
'Mr O'Brien also refused a request for the stable lad to be interviewed by the stewards so the matter has been referred to the British Horseracing Authority under Rule B 83, which states that persons must comply with any instruction given by stewards at a race meeting.'