An International Cycling Union policy of retesting stored doping samples has led to a third rider being provisionally suspended pending a disciplinary case.
The UCI says mountain biker Blaza Klemencic of Slovenia tested positive for EPO in a sample given in March 2012.
The 35-year-old Klemencic competed in women's mountain bike cross-country at the past two Olympics.
Klemencic, a two-time world championship medallist in mountain bike marathon racing, is the third rider suspended in the past five weeks for samples given at least three years ago.
Giampaolo Caruso of Italy and Russian Alexey Shmidtm, both road racers, also tested positive for EPO, a banned endurance-boosting hormone.
In Caruso's case, the UCI said his sample had been "stored and was reanalysed in light of new scientific developments".