Belgian team Quick Step, which includes former world champion Tom Boonen and Olympic and reigning world champion Paolo Bettini, confirmed a physiotherapist belonging to the team was among the people held for questioning.

"I don't know who it is as the prosecutors don't want to reveal any identity. We are waiting to have his name before issuing a statement," Quick Step spokesman Alessandro Tegner said.

"I have just spoken to Tom Boonen a few moments ago and, as far as he was concerned, there have been no raids on his house," said Tegner.

"I have also spoken to some other riders and they have been training and unaware of anything going on. We will have to wait and see what the prosecutors say."

Quick Step was plunged into controversy when ex-rider Johan Museeuw, a former world champion, admitted at the start of this year that he had used drugs to enhance his performance.

Museeuw, currently public relations officer for the team, faces a criminal trial later this month.

Tour champion no longer

Meanwhile, The Tour de France no longer considers Bjarne Riis the winner of the 1996 race after the Danish cyclist admitted having used performance-enhancing drugs.

"We have removed him from the list'' because of the doping admission, Tour spokesman Philippe Sudres said Thursday.

"We consider philosophically that he can no longer claim to have won."

He noted, however, that it is up to cycling's governing body, the UCI, to formally revoke Riis' Tour title, which would be a first in the race's 104-year old history.

Bjarne Riis: Disgraced [GALLO/GETTY]

Riis, now retired, admitted last month that he used the blood-booster EPO from 1993-98, including during his '96 Tour victory, confirming years of speculation that he benefited from banned substances.

Last year's winner, American Floyd Landis, faces losing his title and being banned for two years after he tested positive for synthetic testosterone at last year's race.