Athletics: Trevor Graham, coach of disgraced Olympic 100 metres champion Justin Gatlin, is being investigated by the International Association of Athletics Federations, the sport's world governing body.
The IAAF confirmed in a statement that it was working with the United States Anti-Doping Agency to examine the activities of Graham, who has worked with a number of athletes found guilty of using performance-enhancing drugs.
The statement said: "If evidence exists, either from the ongoing BALCO investigation or otherwise, that Graham has engaged in doping practices in breach of IAAF Rules, disciplinary proceedings will be initiated against him through USADA."
Gatlin faces a lifetime ban after testing positive for testosterone if he is found to have committed a second drug violation.
Graham - banned from US Olympic Committee training facilities last week - prompted the investigation into the Bay Area Laboratory Co-Operative when he anonymously mailed a syringe containing the steroid THG, which had been chemically modified to elude testers.
The statement continued: "The IAAF would like to underline the fact that, notwithstanding the investigation into Graham's activities, the eligible athletes whom he coaches remain free to compete in the remaining World Athletics Tour meetings in 2006 upon invitation from the relevant meeting organisers.
"The IAAF remains totally committed to the fight against doping. In order to defend the credibility of our sport, we will engage all our efforts, in co-operation with partners such as USADA, to defend the majority of athletes who are clean, against athletes, coaches, managers or any other support personnel who break our anti-doping rules."