French 3,000 metre steeplechase specialist Ophelie Claude-Boxberger said she failed to understand how she tested positive for EPO.
Claude-Boxberger, 31, is under investigation by Paris' Public Prosecutor's Office into offences under anti-doping and poisonous substances legislation following a report from the French anti-doping agency (AFLD).
"I have asked for the B sample to be analysed before knowing if it confirms things and I am trying to understand how this product ended up being found in my body," she said on her Facebook page.
"The authorities are currently investigating the people around me, in particular during my training camp in Font-Romeu, to gain information around the only three people close to me who could be questioned."