Pierre Bordry, who heads the French anti-doping council, said the lab found that testosterone in Landis' urine samples came from an outside source.
"I have received a text message from Chatenay-Malabry lab that indicates the 'B' sample of Floyd Landis' urine confirms testosterone was taken in an exogenous way," Bordry told The Associated Press.
The revelation could damage Landis' defense prospects. He has claimed the testosterone in his body was "natural and produced by my own organism."
The American cyclist's backup "B" sample came back positive Saturday, confirming the original "A" test.
Landis could be stripped of the Tour title and banned for two years.
Testosterone, a male sex hormone, helps build muscle and improve stamina. The urine tests carried out on Landis after his victory in the Tour's 17 stage turned up a testosterone/epitestosterone ratio of 11:1 — far in excess of the 4:1 limit.
A report this week in the New York Times cited an unidentified source from the UCI as saying an analysis of Landis' first sample by carbon isotope ratio testing had detected synthetic testosterone, which indicated it had been ingested.
Jacques De Ceaurriz, the head of the Chatenay-Malabray lab, said the isotope testing procedure involving a mass spectrometer is totally reliable.
"It's foolproof. This analysis tells the difference between endogenous and exogenous," he told the AP. "No error is possible in isotopic readings."
Landis spokesman Michael Henson disputed that.
"There is no conclusive evidence that shows that this test can show definitively the presence of exogenous testosterone," Henson said.
But World Anti-Doping Agency chief Dick Pound said the tests were scientifically valid.
"The overwhelming scientific consensus would hold these tests are reliable and what they found is what they found," he told the AP. "Had there been any scientific difficulties or technical difficulties we would have heard about it."
Pound said confirmation of the synthetic testosterone finding would undermine any Landis defense.
"It's probably a very good preemptive move to close down yet another avenue of complaint or argument," he said. "The science is pretty well accepted. The history of these tests are pretty well established." blog comments powered by Disqus