JOIN USFormer double world sprint champion Tyson Gay and former world record holder Asafa Powell failing drug tests has delivered a further body blow to his troubled sport.
Gay has run the fastest three 100 metres of the year and his clash with Jamaica's Olympic 100 and 200 champion Usain Bolt would have been the highlight of the championships.
Instead he has withdrawn from Friday's Diamond League meeting in Monaco and the World Championships on the worst day of a bad week for the central sport of the Olympic Games.
Also on Sunday, Powell and Olympic 4x100 metres relay silver medallist Sherone Simpson said they had both tested positive for the stimulant oxilophrine at last month's Jamaican championships.
Oxilophrine has similar properties to ephedrine, although it has a different chemical structure, and both are on the World Anti-Doping Agency banned list.
Powell, 30, who has been in good form recently said he had not wilfully taken supplements or substances that broke any rules. "I am not now, nor have I ever been, a cheat," he said in a statement.
Simpson, 28, who finished equal second in the 100 metres at the 2008 Beijing Games and won a gold medal in the 2004 Athens 4x100 metres relay, also denied knowingly taking a banned substance.
Earlier sources close to Jamaican athletics said five athletes, including two Olympic medallists, had tested positive for banned performance-enhancing drugs at the championships.
The managers for Bolt and world 100 metres champion Yohan Blake said their athletes were not involved. Blake did not compete at the championships because of injury while Bolt won the 100 metres.
Jamaica, the sunlit Caribbean island which currently dominates world sprinting, was hit by another doping scandal last month when twice Olympic 200 metres gold medallist Veronica Campbell-Brown was suspended by her national federation after a positive test for a banned diuretic.
Gay's admission came in a week when media reports said that up to 30 Turkish athletes faced doping bans after the International Association of Athletics Federations (IAAF) confirmed the country had been targeted over concerns about abnormal biological passport values. Biological passports track changes in athletes' blood profiles which could be caused by doping.
Gay, 30, told two reporters in a telephone conference call that he had been notified by the US Anti-Doping Agency (USADA) on Friday that his A sample from an out-of-competition test on May 16 had returned a positive.
"I don't have a sabotage story. I don't have lies ... I basically put my trust in someone and I was let down," said Gay.
Gay's announcement comes a quarter of a century after Ben Johnson tested positive for a steroid following his victory in the Seoul Olympics 100 metres, still the biggest scandal to hit the Olympic Games.
The 100 metres has been particularly afflicted by dope busts with eight of the fastest 14 men ever having served, or about to serve drug, suspensions.
The IAAF said Sunday's announcements showed its anti-doping procedures were working. "The IAAF's commitment to anti-doping in athletics is unwavering because we have an ethical obligation to the majority of athletes who believe in clean sport," it said in a statement.
"It is for them that we have built a programme that is well resourced, far reaching and sophisticated. The fact that we are able to detect and remove from the sport athletes who have breached our anti-doping rules should be seen in this context.
"The credibility of our anti-doping programme, and the sport of athletics, is enhanced, not diminished, each time we are able to uncover a new case and we have the committed support of every athlete, coach or official who believes in clean sport."
However, Paul Swangard, the marketing director at the Warsaw Sports Marketing Centre at the University of Oregon, told Reuters that the positive tests were a blow to the sport's image. "For our sport, this is the only time we get into the headlines and that negative publicity can't help the sport in the long term," he said.
"From a marketing standpoint, it is another case where the only time mainstream sports audiences are going to hear about this sport is in a negative context. That just sets the sport back."
List of sprinters who have been involved in doping scandals over the last 25 years:
n Ben Johnson (Canada): Stripped of his 100 metres gold medal at the 1988 Seoul Olympics after testing positive for banned steroids. Still the biggest scandal to hit the Olympic Games.
n Linford Christie (Britain): At 32, the oldest man to win gold in the 100 metres with victory at the 1992 Barcelona Olympics. Seven years later, in semi-retirement, tested positive for the steroid nandrolone.
n Dennis Mitchell (US): The American, who won gold as part of the US 4x100 metres relay team at the 1992 Barcelona Olympics, was banned for two years in 1998 for excessive levels of the male sex hormone testosterone.
n Dwain Chambers (Britain): Finished fourth in the 100M final at the 2000 Sydney Olympics but was banned for two years in 2003 after testing positive for the designer steroid THG in the BALCO laborary scandal.
n Tim Montgomery (US): Also implicated in the doping scandal that engulfed the San Francisco laboratory. The American set a 100 metres world record of 9.78 in 2002 but later admitted to doping at the 2000 Sydney Olympics.
n Marion Jones (US): Montgomery's partner and the biggest victim of the BALCO scandal, Jones became the first woman to win five track and field medals at a single Olympics (Sydney 2000). After years of denial, she confessed to being a drugs cheat and was jailed for lying to federal investigators.
n Kelli White (US): Another BALCO victim who admitted to using a cocktail of drugs after winning the 100-200 double at the 2003 Paris world championships.
n Justin Gatlin (US): The American, who won gold in the 100M at the Athens Olympics, has served two doping bans, including four years for excessive levels of testosterone. Won bronze at the 2012 London Olympics.
n Veronica Campbell-Brown (Jamaica): Twice Olympic 200 metres champion who is currently suspended after testing positive for a banned diuretic at a meeting in May this year.
n Sherone Simpson (Jamaica): Gold medalist at the 2004 Olympics in Athens and a silver medalist last year in London as part of Jamaica's 4x100 metres relay teams, Simpson tested positive for the banned stimulant oxilophrine at last month's Jamaican championships.
n Tyson Gay (U.S.): Completed a memorable sweep of sprint tiltes at the 2007 World championships in Osaka when he won the 100 and 200 metres and was part of America's triumphant 4x100 metres relay team. Tested positive for a unidentified substance in an out-of-competition test in May this year.
n Asafa Powell (Jamaica): Held the 100M world record between 2005 and 2008. Tested positive for oxilophrine at the national championships last month.
n Katerina Thanou/Kostas Kenteris (Greece): Thanou (100 metres silver medallist in Sydney) and her Greek team mate Costas Kenteris (Sydney 200 metres champion) were accused of faking a motorcycle crash just before the 2004 Athens Olympics to skip a dope test.
n Merlene Ottey (Slovenia): Jamaican-born sprinter who won world 200 titles but was banned from the 1999 Seville World athletics championships after a positive test for nandrolone. Later cleared by the International Association of Athletics Federations.
n Katrin Krabbe (Germany): Double sprint champion at the 1991 World championships in Tokyo who never competed at an Olympics after a ban for the anabolic agent clenbuterol.