The International Cycling Union has asked national federations in four countries including Australia to investigate riders and officials based on claims of doping made by Floyd Landis.
The UCI says the probes did not "in any way" imply they believed Landis' accusations.
The UCI said the investigations concern Australia's Matthew White, Belgium's Johan Bruyneel - longtime team manager of Lance Armstrong - Canada's Michael Barry and France's John Lelangue to establish if they broke anti-doping rules.
Landis alleged Bruyneel and Armstrong tried to cover up a failed drug test in 2001 by the seven-time Tour de France winner.
Landis, who was stripped of the 2006 Tour title, recently admitted doping throughout his career.