German cyclist Patrik Sinkewitz, suspended for a year after a positive drugs test last June, could face a prison sentence if he persists in concealing the names of others guilty of doping offenses.

A report in Monday's edition of Der Spiegel, quoting sources close to the case, say German criminal investigators looking into the allegations of improper doping practices at the private University Clinic Freiburg are starting to "lose patience with Sinkewitz.”

The former T-Mobile rider has been interviewed for the third time by investigators wanting details about other riders, but Sinkewitz reportedly continues "to want to speak only about what he did,” according to Der Spiegel.

Sinkewitz could be placed in police custody and, in the long term, given a custodial sentence if convicted of withholding evidence, the paper reported.

In the article, which appears under the headline "The Mafia never forgets" Sinkewitz's situation is likened to that of a Mafia informer with the cycling community closing ranks and leaving him in an impossible situation.

"He believed that by confessing only to his actions, he would be able to just reveal what he did and spared from denouncing his former teammates and protecting his ability to rejoin another team once his ban in served," the article continued.

A routine drugs test last June in training for the 2007 Tour de France found Sinkewitz had abnormal levels of testosterone.

He appeared before a German cycling union (BDR) disciplinary committee last year and confessed to doping offenses, including using the banned blood booster erythropoietin (EPO) during the 2006 Tour.

In a November 2007 article in Der Spiegel, Sinkewitz confessed to having used EPO since 2003.

In July 2006, former Tour de France winner Jan Ullrich was barred from competing in the Tour after being linked to the Operación Puerto Spanish doping scandal, which has recently been re-opened after being shelved by the Spanish authorities.

The Sinkewitz affair proved pivotal in the decision of German telecommunications giant Deutsche Telekom, T-Mobile's parent company, to withdraw their sponsorship of the cycling team at the end of 2007.