“The athlete tested positive for EPO following a no-notice test in Kenya.”

Watch: Jemima Sumgong win Olympic gold in Brazil

The IAAF did not respond when asked for confirmation of the report early on Friday.

Sumgong starred at the London Marathon last year, defying the odds to win despite suffering a bruising fall.

Jemima Sumgong dodges protester to win first Olympic marathon gold for Kenya

Steeled by her success in London, she then became the first Kenyan woman to win Olympic marathon gold in Rio.

Sumgong defeated Ethiopia’s world champion Mare Dibaba to confirm her status as the world’s number one marathon runner of the year.

Watch: Jemima Sumgong’s fall during the 2016 London Marathon

Before claims of a positive drugs test emerged, Sumgong said she was looking forward to returning to London to defend her title on April 23.

“London is the marathon every runner wants to win,” she said. “I can’t wait to return to defend my title.”

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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, but said that “if true, they indicate that we are gaining ground in our long-standing fight against doping”.

At the Rio Olympics, Sumgong defied high temperatures to claim an historic gold medal in a race which finished at the city’s famed Sambodromo.

“It was very hot, but everybody had to get through the heat. I had to control my body and listen to my body very carefully,” said Sumgong, who added that victory made up for her disappointing showing at the 2008 Beijing Olympics.

“I was in Beijing but I was pretty disappointed that I wasn’t able to win a medal or make it on the podium, but I knew one time, one day, I’d be somewhere.

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“I was never worried that I’d lose this. At the 40km 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 stop doping, which has tarnished their image, in which they agreed 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.

In July last year, an investigation by German television channel ARD and Britain’s Sunday Times newspaper alleged that doping is rife at the elite training centre in Iten.

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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.

Athletics Kenya chief Jackson Tuwei warned that any athlete who failed to comply would not be selected to represent Kenya 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 wrote on Twitter.