The International Association of Athletics Federations has sent drugs tests for several athletes to Lausanne, Switzerland for further study.
One of those athletes is Russian Olga Yegorova, who recently tested positive for the banned hormone EPO.
The tests were completed just before the world championships started last week. The tests are looking for the banned hormone EPO among other substances.
Russian Olga Yegorova had tested positive for the banned hormone after a Golden League meet in Paris. However, the IAAF decided that the test in Paris did not conform with international standards and the result was overturned. That meant that Yegorova could run in the world championships.
The head of the IAAF medical commission, Arne Ljungqvist, says Yegorova was tested again right before the championships began and her test has been sent along as well.
"In her particular case," he said, "since she tested positive for urine on the urine sample in Paris, we have sent her urine test along as well, irrespective of any deviation or whatever because we have to have a full test on her."
The test results are expected around midday Thursday, just before Yegorova is scheduled to run in the qualifying for the women's five-thousand meters race.
Reigning world champion Gabriela Szabo of Romania had threatened to pull out of the race if Yegorova were allowed to run. However, Wednesday after consulting her husband and her coach, she said she would take part in the race.