Undercover reporters visited the world 100 metres champion's training camp in Florida, where members of his team are said to have offered to illicitly supply performance-enhancing drugs.
When confronted about those statements, Gatlin's agent said he was just playing along because he wanted to convince the reporters to buy the drugs.
Gatlin, 35, has been banned twice - in 2001 after testing positive for amphetamines, and in 2006 for synthetic testosterone.
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Justin Gatlin is reportedly being investigating by anti-doping authorities.
"These allegations are very serious and strike at the heart of the integrity of athletics", he said.
Gatlin stunned the world when he beat world record holder Usain Bolt in his final individual outing. Their reporter (whose face was pixelated in a photo in the story) cozied up to Mitchell and Wagner under the guise of trying to obtain PEDs to make their star look more like a real life track star.
Mitchell and Wagner are said to have claimed that the use of banned substances in athletics is still widespread - with the agent even saying that Gatlin himself had been taking performance-enhancing drugs.
In July, Gatlin won the 100 meters at the world championships in London in what was former world champion Usain Bolt's last competitive race. "We are presently coordinating with the Athletics Integrity Unit in order to investigate these claims fully".
Lord Coe, the IAAF president, said: 'These allegations are extremely serious and I know the independent Athletics Integrity Unit will investigate in accordance with its mandate'.
"Under the IAAF Rules, all athlete support personnel - agents, coaches etc - are bound by both the IAAF anti-doping code and IAAF integrity code of conduct. We are working with member federations on how we move to an official accreditation system for support personnel so athletes have choices and assurance in those choices".