US prosecutors on Monday said 27 trainers, veterinarians and others have been criminally charged in a wide-ranging scheme to drug race horses. Among those charged was Jason Servis, the trainer of Maximum Security, one of the world's best racehorses. Prosecutors accused him of covertly administering performance-enhancing drugs "to virtually all of the racehorses under his control". Maximum Security appeared to win the 2019 Kentucky Derby before being disqualified for interference. He continues to race, and won last month's $20 million (Dh74m) Saudi Cup, the world's richest horse race. Servis could not immediately be reached for comment. The charges were unveiled in four indictments accusing the defendants of involvement in a drug alteration and misbranding conspiracy. Some defendants also face smuggling and obstruction charges. Prosecutors said illegal drugs were administered to horses to help them run faster, and concealed the doping from regulators. They said races were affected in such places as New York, New Jersey, Florida, Kentucky, and Ohio. Prosecutors said doping can reduce horses' sensitivity to pain, which can cause horses to overexert themselves and lead to injuries or death. Horse racing has long been tainted by allegations that horses were given drugs to improve their performance on the track. Critics, including animal rights advocates, have called for changes in the industry, or banning racing altogether, following a recent rash of horse fatalities. These include several dozen deaths at southern California's Santa Anita Park since the middle of 2018. Servis entered horses in approximately 1,082 races between 2018 and last month. Another trainer who was charged, Jorge Navarro, entered horses in 1,480 races over that time, prosecutors said.