American sprinter LaTasha Jenkins has failed a drugs test, the Chicago Tribune said on its website on Thursday.
Her "A" sample from an in-competition test in late July was found to contain traces of the anabolic steroid nandrolone, the newspaper said, quoting unnamed sources.
Jenkins, the 2001 world indoor 200 metres silver medallist, could not be reached for comment but her coach Trevor Graham denied the Tribune report.
"That is not true," Graham said.
Jenkins, 28, has experienced knee problems recently and has flown home to Raleigh from Europe, Graham said.
Graham's attorney, Joseph Zeszotarski, later released a statement saying the coach had no knowledge of any issue involving Jenkins until informed of the Tribune report.
"We are attempting to contact her to hear her explanation for this report," the statement said.
The International Association of Athletics Federations (IAAF) and USA Track & Field (USATF) would not comment on the Tribune story.
Zeszotarski disputed the Tribune's report that Jenkins was the 11th athlete coached by Graham to test positive.
"Of the previous 10 athletes at issue, only Justin Gatlin tested positive while being coached by Trevor," Zeszotarski said in the statement to reporters.
It has been reported that at least eight athletes coached by Graham, including former Olympic champion Marion Jones, have committed doping offences or tested positive.
Gatlin announced last month he had tested positive for the male sex hormone testosterone or its precursors. The Olympic and world 100 metres champion was banned for up to eight years on Tuesday after agreeing that his positive test constituted a doping violation.
Jones, who won five medals at the 2000 Olympics while coached by Graham, failed an initial drugs test for the banned blood-boosting drug erythropoietin (EPO) at the US championships in June. Her "B" sample has yet to be tested.
She left Graham's training camp in late 2002.
Gatlin and Jones have denied knowingly taking performance-enhancing drugs.
Graham has denied providing banned substances to his athletes. He is being investigated by the IAAF and USADA, the IAAF has said.
He has also been banned by the US Olympic Committee (USOC) from using its facilities because of the number of doping offences or positive tests by his athletes.