Jemima Sumgong, the first Kenyan woman to win an Olympic gold in the marathon when she triumphed in Rio last year, has failed an out-of-competition dope test, athletics officials said Friday.
The 32-year-old, who is also the reigning London Marathon champion, tested positive for the banned blood booster EPO in a test by the International Association of Athletics Federations (IAAF) in her native Kenya.
"The IAAF can confirm that an anti-doping rule violation case concerning the athlete Jemima Jelagat Sumgong (Kenya) has commenced this week," the IAAF said.
"The athlete tested positive for EPO following a no-notice test conducted by the IAAF in Kenya," the sport's ruling body added.
"This was part of an enhanced IAAF out-of-competition testing programme dedicated to elite marathon runners which is supported by the Abbott World Marathon Majors group. The IAAF will make no further statement about this case until its conclusion."
Sumgong starred at the London Marathon last year, defying the odds to win despite suffering a bruising fall.
Steeled by her success in London, she then became the first Kenyan woman to win Olympic marathon gold, defeating Ethiopia's world champion Mare Dibaba in Rio to confirm her status as the world's top marathon runner of 2016.
Before claims of a positive drugs test emerged, Sumgong vowed to defend her London title on April 23.
But Tim Hadzima, general manager at Abbott World Marathon Majors, organiser of the world's largest marathons including London, said the organisation was "distressed" by the reports, adding: "if true, they indicate that we are gaining ground in our long-standing fight against doping".
At the Rio Olympics, Sumgong defied temperatures of 28 degrees Celsius (82F) to claim an historic gold medal in a race that finished at the city's famed Sambodromo.
"I was never worried that I'd lose," said Sumgong, who added that victory made up for a disappointing showing at the 2008 Beijing Olympics. "At the 40 kilometre mark I knew the gold was mine."
Earlier this year, Sumgong was one of a number of top Kenyan athletes who welcomed a new initiative to eradicate doping, which has tarnished their image, agreeing to be monitored by doctors appointed by the IAAF and Athletics Kenya.
"It will be easy for us now to communicate with these doctors before we take any medicine when the need arises," said Sumgong.
The move came after an investigation by German television channel ARD and Britain's Sunday Times newspaper last July alleging that doping was rife at the elite training centre in Iten.
Sumgong's former training partner, the 2014 Chicago and Boston Marathon champion Rita Jeptoo, is serving a four-year ban after also testing positive for EPO.
Kenyan athletics boss chief Jackson Tuwei has warned that any athlete who failed to comply would not be selected to represent the country in international competitions.
"Forty-nine athletes have been found to have violated the Wada (World Anti-Doping Agency) code in the past five years but were cautioned according to the laws of the land and Wada code," said Tuwei.
News of Sumgong's test was welcomed by other athletes. US distance runner Emma Coburn, a bronze medallist in the 3,000m steeplechase at last year's Olympics, applauded the IAAF's out-of-competition testing.
"Out of competition testing is so important!! Well done, IAAF. I hope to see more productive results from no-notice out of competition tests," Coburn tweeted.