(CNN) -- Elite sprinters Tyson Gay and Asafa Powell tested positive for banned substances on a day of shame for athletics. 

Gay, a former world champion from the U.S., said Sunday he was told by the U.S. Anti-Doping Agency that an A sample from an out of competition test taken in May came back positive. 

Later Sunday, Powell, a former world-record holder from Jamaica, said he was caught for using the banned stimulant oxilofrine that showed up in a test at last month's Jamaican trials. 

Jamaica's Sherone Simpson, too, revealed she was caught for doping. 

Gay didn't name the substance found in his system and added that he never knowingly took performance-enhancing drugs. He pulled out of next month's world championships in Russia. 

"I don't have a sabotage story," Gay was quoted as saying by Reuters. "I basically put my trust in someone and was let down. I made a mistake. 

"I know exactly what went on, but I can't discuss it right now." 

Gay and Powell, both 30, become the second and third high-profile track stars in a month to be embroiled in a doping scandal. 

Two-time Olympic 200-meter champion Veronica Campbell-Brown was provisionally suspended in June after she tested positive for a banned substance. 

The Jamaican sprinter reportedly had traces of a banned diuretic, which is used as a masking agent, in a sample she provided to testers at Jamaica's International Invitational World Challenge in May. 

British newspaper The Guardian reported the banned diuretic was from a cream she was using in an attempt to recover from a leg injury. 
Who was suspended in June?
For what?
Where is she from?
Is she a champion?
Of what game?
For which event?
Did she only win once?
How many time?
What kind of substance showed up in her test?
Where did it come from?
When?
What was she getting over?
Was she using a cream?
What was in it?
Did Asafa Powell fail her test?
What did they find in her test?
Where is she from?
Did Tyson Gay pass his?
Was he sabotaged?
What was Sherone Simpson found to be doing?
Veronica Campbell-Brown
Veronica Campbell-Brown was provisionally suspended in June 
Testing positive for a banned substance
 after she tested positive for a banned substance
Jamaica
The Jamaican sprinter
Yes
Two-time Olympic 200-meter champion Veronica Campbell-Brow
Olympic Sprinting
Two-time Olympic 200-meter champion Veronica Campbell-Brown 
200-meter
Olympic 200-meter
No
Two-time Olympic 200-meter 
Two
Two-time Olympic 200-meter champion Veronica Campbell-Br
Diuretic
he Jamaican sprinter reportedly had traces of a banned diuretic
A sampl  provided to testers
in a sample she provided to testers at
May
in a sample she provided to testers at Jamaica's International Invitational World Challenge in May
Leg injury
British newspaper The Guardian reported the banned diuretic was from a cream she was using in an attempt to recover from a leg injury
Reportedly, yes
British newspaper The Guardian reported the banned diuretic was from a cream she was using
The diuretic
British newspaper The Guardian reported the banned diuretic was from a cream 
Yes
Asafa Powell tested positive
Oxilofrine
Powell, a former world-record holder from Jamaica, said he was caught for using the banned stimulant oxilofrine
Jamaica
Later Sunday, Powell, a former world-record holder from Jamaica
No
Tyson Gay and Asafa Powell tested positive
No
"I don't have a sabotage story,
Doping
Sherone Simpson, too, revealed she was caught for doping