There is more doping in athletics now because the potential prize money available is "bigger than ever", according to a former US sprinter who was himself banned from the sport in 2005.
Tim Montgomery was speaking after a decision today to ban the Jamaican sprinter Asafa Powell for 18 months after he tested positive for the stimulant oxilofrine.
Montgomery said he could not see why an athlete would "go into a competition not knowing what they're taking".
More top news
A member of FIFA's Executive Committee believes Qatar will be stripped of the 2022 World Cup because of concerns about the soaring heat
Anti-discrimination campaigners have offered their support to Mario Balotelli after he received a tide of racist abuse on Twitter
Nasa's Maven spacecraft enters into the orbit of Mars after a 10-month, 442 million-mile journey.