The British Horseracing Authority is investigating a £35,000 race at Wincanton on Saturday - as the winner may not have been qualified to run.
The Young Master, ridden by Barry Geraghty, won the Badger Ales Trophy by seven lengths from Court By Surprise.
The conditions of the race said that the Neil Mulholland-trained five-year-old needed to have competed in three steeplechases in Britain, Ireland or France to be permitted to line up.
But the horse had only competed in two.
A spokesman for the Authority says that the owner of the runner-up, Court By Surprise, has the option to object, or, alternatively, officials could lodge an objection.
All entries are made by trainers to the Authority's administration centre, run by Weatherbys.
Although a disqualification is possible, it will not affect bets which are settled on the way the runners went past the post.