Kenya's athletics authorities say they are investigating allegations of widespread doping in the country.
There have been media allegations that doctors had given banned substances to runners at a high-altitude Rift Valley training base.
In June, distance runner Mathew Kisorio failed a drugs test at Kenya's national championships and said doping was rife.
Athletics Kenya head Isaiah Kiplagat said most athletes were "clean", but that he took the claims seriously.
"We are carrying out an investigation," he told the BBC. "We are working with other authorities to ensure that we uncover if this true, and then take action appropriately on the culprits."
Kisorio, who ran the fourth-fastest half-marathon time ever in 2011, was suspended after testing positive for an anabolic steroid in June.
He subsequently alleged that many of his fellow Kenyan athletes were doping.