The 2006 Tour de France winner Floyd Landis has been sacked by his Swiss Phonak team after a second drugs test revealed abnormally high levels of testosterone.
Zurich-based Phonak dismissed the United States rider on the grounds of "violating the team's internal code of ethics" after laboratory tests on his B sample on Saturday backed up earlier findings.
"Team owner Andy Rihs deeply regrets this development," Phonak said in a statement.
"Landis will continue to have legal options to contest the findings. However, this will be his personal affair and the Phonak team will no longer be involved in that."
Landis could now become the first Tour de France winner to be stripped of his title for doping offences and also faces a two-year ban from the sport.
Tour de France director Christian Prudhomme told the Associated Press news agency that Landis was no longer considered champion, but the decision to strip him of his title rests with the International Cycling Union (UCI).
The UCI has so far only released the results of the test.
"The analysis of the sample B of Floyd Landis's urine has confirmed the result of an adverse analytical finding notified by the anti-doping laboratory of Paris on July 26," the UCI said in a statement.
Landis has consistently denied cheating after pulling off a remarkable win in cycling's premiere event.
Landis fights back
"I have never taken any banned substance, including testosterone," Landis said in a statement on Saturday. "I was the strongest man at the Tour de France, and that is why I am the champion.
"I will fight these charges with the same determination and intensity that I bring to my training and racing. It is now my goal to clear my name and restore what I worked so hard to achieve."
Landis' lawyer is preparing to take the case to arbitration, said a statement issued by his spokesman, Michael Henson.
The rider took the 17th stage of the race last month after a disastrous 16th stage in which he fell back from first to 11th place.
Four days after his victory, Landis's urine sample showed up a testosterone-epitestosterone ratio of 11:1, compared to the normal human measurement of 1:1 or 2:1.
The 30-year-old US rider has since claimed that he has naturally high levels of testosterone that could have been magnified by alcohol he consumed after the race.
Phonak, a firm that manufacturers hearing aids, has already ended its association with the sport following a series of high profile doping scandals to affect the team.
In the past two years seven of the team's riders have been implicated in doping cases. Oscar Camenzind and Tyler Hamilton were among those who tested positive for banned substances.
swissinfo with agencies
The 93rd Tour de France featured 20 stages.
The final stage between Sceaux-Antony and Paris was won by Norway's Thor Hushovd.
Final standings (at present): 1. Floyd Landis 2. Oscar Pereiro (Spain) +59 seconds. 3. Andreas Klöden (Germany) + 1:29
On July 27 it was announced that a test on Landis after Stage 17 on July 20 showed an "unusually high" level of testosterone in his urine.
On August 1 reports said synthetic testosterone had been found, throwing doubts on his claims that it was a natural occurrence.
In March 2006 Swiss Phonak rider Sascha Urweider was suspended following a positive test for high levels of testosterone.
In 2004 three Phonak riders were all found guilty of doping violations and fired: Tyler Hamilton and Santiago Perez (blood doping) and Oscar Camenzind (EPO).