The People for the Ethical Treatment of Animals are urging prosecutors to bring animal cruelty charges against Eight Belles' trainer, Larry Jones.

Lawyers for the animal rights group plan to deliver a letter to R. David Stengel, Commonwealth's Attorney for Jefferson County, on Thursday asking for an investigation to be launched into the death of the 3-year-old filly. Eight Belles was euthanized moments after the Kentucky Derby on May 3 after breaking both of her front ankles.

PETA said Jones' admission that he gave Eight Belles an anti-inflammatory drug less than two days before the Derby jeopardized her safety.

Jones has denied any wrongdoing in the handling of the horse, and said Wednesday that he followed the rules of racing as set forth by the Kentucky Horse Racing Authority.

An autopsy on Eight Belles completed last month showed she had no diseases or pre-existing bone abnormalities before her breakdown. She also tested negative for steroids.

A call to the Commonwealth's Attorney in Jefferson County by the Associated Press was not immediately returned.