The German winner of the 1997 Tour de France and his Spanish teammate were suspended by their T-Mobile team just before the current Tour after being linked, with more than 50 other cyclists, to the Operation Puerto investigation.

The prosecutor's office here, where T-Mobile has its head office, said it had opened its own investigation into the matter in response to a fraud complaint lodged by an academic and former athlete.

"The procedure arises following the lodging of a complaint for fraud and breaches of the law concerning medications," said prosecutor Monika Nostadt-Ziegenberg.

"The complaint was lodged on July 7 and is going to be examined."

There is no law against doping in Germany but Britta Bannenberg, a professor at Bielefeld university in the country's west, charged that "Jan Ullrich has hidden from T-Mobile that he used illicit substances that were procured thanks to his salary and bonuses."

The rider's long-time mentor, Rudy Pevenage, sacked as T-Mobile's Tour sporting director, was also named in the writ.

Ullrich, Sevilla and seven other riders were excluded from the Tour, after Spanish authorities sent evidence to race organisers incriminating them in an alleged blood-boosting and doping service run by cycling doctor Eufemiano Fuentes.

The pair protested their innocence and vowed to furnish evidence that proved they were not involved with Fuentes.

But they failed to meet a T-Mobile ultimatum to provide the evidence by July 15, and two days later Ullrich released a statement suggesting he should be considered innocent until proven otherwise.

He said his lawyers had asked the Spanish authorities for clarification of the evidence against him.