The International Association of Athletics Federations says seven athletes who competed at the world championships in Moscow last month failed doping tests and have already been sanctioned or provisionally suspended.
Three competitors tested positive for EPO: race walkers Ayman Kozhakhmetova of Kazakhstan and Ebrahim Rahimian of Iran, and marathon runner Jeremias Saloj of Guatemala.
A steroid was found in the urine samples of javelin thrower Roman Avramenko of Ukraine, and sprinters Yelena Ryabova of Turkmenistan and Elyzaveta Bryzgina of Ukraine.
Afghani sprinter Massoud Azizi tested positive for a metabolite of nandrolone.
The IAAF says 538 athletes had their urine tested during the worlds, and 132 before the event.