Rio de Janeiro Olympic marathon silver medallist Eunice Kirwa of Bahrain and Milan Erzen are under investigation for suspected doping.
Kirwa has been provisionally suspended by the Athletics Integrity Unit (AIU) after testing positive for erythropoietin (EPO), a banned blood-boosting hormone that improves endurance.
Meanwhile, Erzen is allegedly being investigated by Union Cycliste Internationale (UCI) in relation to an inquiry into a blood doping ring dubbed Operation Aderlass.
However, he denied any involvement.
“All and any implications regarding my involvement in Aderlass are absolutely false and unfounded,” Erzen said.