US rider Tom Danielson has been suspended by Cannondale-Garmin after a positive test for synthetic testosterone, the American team confirmed on Monday.
Danielson, 37, revealed himself on his Twitter account that he had been informed of the positive test carried out on July 9 by the US anti-doping agency (USADA).
"I have not taken this or any other banned substance," insisted Danielson, who has requested that the "B" sample be tested and blamed possible contamination by food supplements.
"I would never ever take anything like this especially after everything I have gone through the last (few) years," he wrote. "This makes absolutely no sense."
Danielson could face a lifetime ban from cycling having previously admitted doping while riding with the Discovery Channel team.
He served a six-month suspension between September 2012 and March 2013, and his results from March 2005 to September 2006 were wiped out.
Danielson, who has ridden for the team of Jonathan Vaughters since 2008, finished eighth in the 2011 Tour de France.
Winner of the Tour of Utah in 2013 and 2014, he was forced to withdraw from this year`s race which runs from August 3 to 9.=