More than 1 in 10 elite athletes may be using banned performance-enhancing substances, according to World Anti-Doping Agency director general David Howman.
"We have some guestimates based on some research undertaken over the last years... It's far more than we would wish it to be - over 10%. That is of concern because those being caught by the system is far lower than that. Not in all sports, in some sports,” Howman told the BBC.
He warned that young athletes may be doping in order to reach elite status. "The area of most concern for us is the level of young athletes who have not broken through into the elite who are trying to get that breakthrough and are susceptible to taking drugs because that's a shortcut.”
"Not only are they susceptible to taking drugs, they are being encouraged to do so by any one of a number of people that surround them - coaches, trainers, even parents - because it's a way to make a lot of money."
While elite athletes are tested regularly, Howman noted that junior athletes often fell "under the radar".