An agent at the centre of doping allegations against world 100 metres champion Justin Gatlin has now claimed he invented a story about obtaining banned drugs in a bid to impress undercover reporters.
Undercover reporters from The Daily Telegraph contacted Mitchell, Gatlin's coach, and his track agent Robert Wagner about obtaining human growth hormone and testosterone.
Wagner was filmed allegedly claiming he could supply drugs and Mitchell is alleged to have spoken about "complex" designer drugs which are unknown to the authorities and do not show in drugs tests.
Wagner is also quoted as having named sport stars using drugs, including both Gatlin and Mitchell.
The duo were targeted by undercover reporters posing as representatives of a film company with a budget of $250,000 (£187,000/€212,000) to secure drugs to make an actor look like an athlete.
Gatlin, booed after returning from two doping suspensions to win the 100 metres title at the International Association of Athletics Federations (IAAF) World Championships in London this year, insists he has done nothing wrong and has taken swift action to distance himself from Mitchell.
"It was just big talk," said Wagner.
"I did not actually source or supply the substances the reporters asked for but stupidly claimed I could.
"I apologise to Mr Gatlin, his management and family for saying completely false things about him and I apologise to other completely innocent athletes also wrongly implicated by my words."
Wagner claims to have reported his meeting with the reporters to the Athletics Integrity Unit (AIU).
He now says he will assist the investigation "in every way I can".
Renaldo Nehemiah, Gatlin's agent, has also since claimed that Wagner had only worked for Gatlin on two or three occasions.
Gatlin, 35, received a two-year ban, reduced on a appeal, after a positive test for amphetamines in 2001 before a second suspension, reduced to eight and then four years, after a failure for testosterone.
He has always denied wrongdoing and attempted unsuccessfully to blame his second failure on a masseuse for rubbing cream containing the banned substance onto his back.
Mitchell, a 4x100m relay gold medal winner at the Barcelona 1992 Olympics, famously blamed a failed test for testosterone in 1998 on "five bottles of beer and sex with his wife at least four times…", adding: "it was her birthday, the lady deserved a treat".
"I am not using and have not used PED's," Gatlin said in a statement published on Instagram.
"I was shocked and surprised to learn that my coach would have anything to do with even the appearance of these current accusations.
"I fired him as soon as I found out about this.
"All legal options are on the table as I will not allow others to lie about me like this."