Olympic 1500m silver medallist Gamze Bulut has been provisionally suspended pending an IAAF investigation into a possible doping violation.
Turkey's NTV television reports that abnormalities were found in Bulut's blood samples from 2011, 2012 and 2013.
The 23-year-old is the fifth 2012 Olympic finalist to face drug allegations, along with fellow Turk Asli Cakir Alptekin.
Alptekin has since been stripped of her gold medal and banned for eight years.
Nataliya Kareiva of Belarus and Russian athlete Yekaterina Kostetskaya, who finished seventh and ninth respectively, have since been banned by the International Association of Athletics Federations (IAAF) for biological passport abnormalities.
Ethiopia-born Swede Abeba Aregawi, who finished fifth in London, was suspended last week pending an investigation after testing positive for a banned substance.