LOUISVILLE, Ky. (AP) — Churchill Downs has suspended trainer Bob Baffert from entering horses at the track and suggested that it would invalidate Medina Spirit's Kentucky Derby victory if the results of a failed postrace drug test are upheld.

The announcement from Churchill Downs came shortly after Baffert held a news conference to announce the failed drug test, which the Hall of Fame trainer vowed to fight "tooth and nail."

Medina Spirit is Baffert's fifth horse to fail a drug test in a year.

The colt won the Kentucky Derby on May 1 by a half-length over Mandaloun.

The only horse to be disqualified for medication after winning the Derby is Dancer's Image in 1968.