Two Kenyan marathon runners have been banned after positive tests for banned substances following suspensions for three other marathoners from the east African nation last month.
Athletics Kenya secretary general David Okeyo says Salome Jerono Biwott and Jynocel Basweti Onyancha have both been suspended for two years.
Last month marathon runners Wilson Erupe Loyanae and Nixon Kiplagat Cherutich were banned for two years while Moses Kiptoo Kurgat was suspended for a year.
Last week German freelance journalist Hajo Seppelt revealed an underground television investigation aired before last year's London Olympics had convinced him there was a widespread doping problem in the country which, along with Ethiopia, dominates distance running.