The world's top female marathon runner, Kenya's Rita Jeptoo, has tested positive for the banned blood-boosting drug EPO during an out-of-competition doping control, Kenya's athletics governing body told AFP Friday. The revelation is likely to be met with shock and disbelief in Kenya, whose distance runners are a major source of national pride. Jeptoo, a three-times winner of the Boston marathon and a two-time champion in Chicago, is also the biggest name in Kenyan athletics ever to have been tested positive. World Marathon Majors (WMM) organisers also said they were postponing the awarding of this year's $500,000 prize to 33-year-old Jeptoo. She had been due to attend the New York marathon on Sunday to collect the prize, the biggest payout in distance running. Athletics Kenya's vice president, Jackson Tuwei, said the International Association of Athletics Federations (IAAF) had revealed a positive 'A' sample test for the blood-boosting drug Erythropoietin (EPO) -- which can massively boost endurance and, crucially, recovery times during high-volume marathon training. "After we received the letter from the IAAF, we summoned Rita Jeptoo for a meeting in Nairobi. She denied having taken any drugs," Tuwei told AFP. "We cannot condemn her. She has a right to contest it" and request that the 'B' sample also be tested, he added. A separate statement from Athletics Kenya, which in recent years has been accused of failing to take sufficient action against drug cheats, also said it was "disappointed" by the finding. Jeptoo could not be reached for comment, but was quoted in Kenyan media as saying allegations that she cheated were "lies". - Best in the world - Jeptoo is currently the world's top female marathon runner, having won the Chicago marathon twice and Boston three times, including in 2013 when she set the course record of 2hr 18min 57sec -- the eighth-best female marathon time of all time. Her last win, in Chicago in October, came weeks after the urine test was carried out -- and secured her overall win of the WMM series, which includes marathons in Berlin, Boston, Chicago, London, New York and Tokyo. She had been due to receive her WMM prize for the 2013-2014 series in New York on Sunday, but organisers said the ceremony had been delayed after the RunBlogRun website broke the news of the positive test. "World Marathon Majors is disappointed to learn that Rita Jeptoo has apparently had an A test that proved positive for a banned substance under IAAF rules," a WMM statement said. "World Marathon Majors has been at the forefront of the fight against doping in our sport and has a rule that no athlete can win the World Marathon Majors Series title, who has been in breach of IAAF anti-doping rules," it added. "At present there has been no decision in this case by the IAAF, including in relation to sanctions, and as a result... it has been decided to postpone the WMM Awards Ceremony." Kenya has been under pressure from the World Anti-Doping Agency (WADA) to take action over doping after 17 of its athletes tested positive between January 2012 and June 2013. But a report from an independent task-force released this year did not uncover any evidence of the use of the drugs among top athletes, and insisted that "the few reported cases were aided and abetted by professional doctors, managers and agents."