ATHENS, Greece (AP) — A Greek prosecutor has charged Olympic champion race walker Athanasia Tsoumeleka with using an illegal performance-enhancing drug.

The offense carries a maximum two-year jail sentence.

Court officials say prosecutor Costas Simitzoglou charged Tsoumeleka on Monday with breaking Greece's doping laws after she tested positive in January for CERA, an advanced version of the blood-booster EPO.

The 27-year-old Tsoumeleka won the 20-kilometer walk at the 2004 Athens Olympics. She tested positive in a retesting of a sample she provided two days before the Beijing Olympics. A backup sample also came back positive.

Tsoumeleka denies knowingly using the substance and has expressed doubts about the procedure.