Ethiopia's anti-doping agency is investigating nine runners, five of which are considered “top athletes,” for suspicious results in doping tests, according to the Associated Press.
Solomon Meaza, head of Ethiopia's anti-doping agency, says the International Association of Athletics Federation is looking into four athletes while his agency investigated the top stars.
"There is a real concern when the upcoming investigations arrive," he said.
No names or banned substances were mentioned.
Ethiopian men and women held the world-leading marks in five track events last year.
Abeba Aregawi, the 2013 world 1,500 meter champion, was born in Ethiopia and switched allegiances to Sweden in 2012. She tested positive for a banned substance and has been suspended until the results of her B-sample are revealed.
Last year, Russia was banned from international competition by the IAAF after the World Anti-Doping Agency determined evidence of systemic doping and cover-ups have taken place in recent years.
- Christopher Chavez