let down." Gay, who won the 100 and 200 metres at U.S. nationals

The list reads like a Whos Who among the worlds best sprinters: Jamaican Asafa Powell, the former world-record holder at 100 metres. American champion Tyson Gay, who went out of his way to promote himself as an anti-drug athlete. Jamaican Sherone Simpson, who has a gold and two silver Olympic medals to her credit. Word came Sunday that all three had failed drug tests. "A sad day," one former track official called it -- and certainly a day that punctured the myth that the oft-troubled sport has cleaned up its act. "I am not now -- nor have I ever been -- a cheat," Powell said in a message released through his Twitter account. The 30-year-old Powell, whose 100-meter record of 9.74 stood until Usain Bolt beat it in 2008, was calling for an investigation as to how a stimulant called oxilofrine entered his system and caused a positive test at Jamaicas national championships in June. Simpson, who tested positive for the same stimulant, said she "would not intentionally take an illegal substance of any form into my system." Gay, the American-record holder in the 100, was more contrite, though he wasnt taking full responsibility. "I dont have a sabotage story. I dont have any lies. I dont have anything to say to make this seem like it was a mistake or it was on USADAs hands, someone playing games," said Gay, who fought back sobs in a telephone interview. "I dont have any of those stories. I basically put my trust in someone and I was let down." Gay, who won the 100 and 200 metres at U.S. nationals last month, said he would pull out of the world championships. The 30-year-old, who won the world championship in the 100, 200 and 4x100 relay in 2007, took part in the U.S. Anti-Doping Agencys "My Victory" program -- in which athletes volunteer for enhanced testing to prove theyre clean -- and his results never raised red flags. Until, that is, an out-of-competition test May 16, where results came back positive for a banned substance, the identity of which neither he nor USADA CEO Travis Tygart would reveal. Gay said his "B" sample will be tested soon, possibly as early as this week. Generally, first-time offenders are hit with two-year bans, though reduced penalties are sometimes given if there are extenuating circumstances, which both Gay and his coach, Lance Brauman, said there were. "He mentioned that he (trusted) someone and th