Olympic marathon champion Jemima Sumgong tested positive for the blood booster EPO in a surprise test in Kenya, the IAAF said Friday, another damaging blow to the credibility of the East African country’s famed distance-running program.

Sumgong became the first Kenyan woman to win Olympic gold in the marathon at last year’s Rio de Janeiro Games, is the reigning London Marathon champion, and was the points leader in the World Marathon Majors series. She was in line to receive a $250,000 bonus when the two-year cycle is completed in Boston on April 17. The series said it won’t name a women’s winner until doping officials have resolved her case.

“The athlete tested positive for EPO following a no-notice test conducted by the IAAF in Kenya,” track and field’s governing body said in a statement.

Sumgong’s test was “part of an enhanced IAAF out-of-competition testing program dedicated to elite marathon runners,” the IAAF said.

Sumgong is now the highest profile of dozens of Kenyan athletes to have failed doping tests since the 2012 London Olympics and her case again puts the country’s anti-doping failures back in the spotlight.

Her failed test follows that of compatriot Rita Jeptoo, who was also the leading women’s marathon runner in the world when she tested positive for EPO in an out-of-competition test in Kenya in 2014. Initially given a two-year ban, Jeptoo’s punishment was doubled to four years in 2016 after the IAAF appealed to the Court of Arbitration for Sport for a sterner sanction.

World Marathon Majors general manager Tim Hadzima said the series was distressed to learn of reports that Sumgong had failed a doping test but that, “if true, they indicate that we are gaining ground in our long-standing fight against doping.”

The World Marathon Majors awards prizes to runners with the top finishes over six of the most prestigious annual marathons, plus the Olympics and world championships.

Sumgong can request that her “B” sample or backup sample is also tested. If that is also positive for EPO she faces at least a two-year ban.

The 32-year-old Sumgong’s victory in Rio capped an outstanding performance by Kenya in track and field at the Olympics, when the country finished second to the United States in the medal table. Eliud Kipchoge also won gold in the men’s marathon for a Kenyan sweep.

But Kenya’s Olympics were also undermined by a series of scandals involving coaches and officials, and its reputation has been seriously harmed by a spike in doping cases over the last five years.