Beijing - Kenyan runners Joyce Zakary and Koki Manunga have failed doping tests at the athletics world championships and are provisionally suspended, ruling body the IAAF said on Wednesday.
The two athletes provided positive samples in target tests in Beijing on August 20 and 21 respectively but the IAAF did not disclose the substance.
It said they have accepted provisional suspensions.
"These targeted tests were conducted by the IAAF at the athlete hotels during the pre-competition phase.
The IAAF will not discuss the details of the cases as they progress through the results management process," the IAAF said.
Zakari won her heat in Beijing in a national record 50.71 seconds but did then not compete in Tuesday's semi-finals.
Manunga went out in second last place in the 400m hurdles heats.
Kenya lead the Beijing medal table with four gold, three silver and two bronze medals - and have a 47-40-34 haul overall at the worlds - but have been the target of doping allegations in recent years and months, with 13 Kenyan athletes currently officially banned by the IAAF.