When the investigation began, Di Gregorio was riding for Astana. He won one stage in the 2011 Paris-Nice race with the Kazahk team. This season, he has had one stage win, in the Spanish Tour of Asturias in April.
Sanquer said he believed Di Gregorio, who recently became a father, ''didn't understand the breadth of what he was doing and the seriousness of what he could be doing'' if the accusations turn out to be true.
''Cycling is about beautiful moments, and there also very difficult ones. This is one,'' Sanquer said. ''There are other things - sickness, injury ... it's part of a series of things that riders have to get through.''
In the 2008 Tour de France, Cofidis pulled out of the race following Italian rider Cristian Moreni's positive test for testosterone.
In 2004, French police arrested then-Cofidis riders David Millar of Britain and Cedric Vasseur of France in another doping investigation involving the team and seized male hormones, EPO and amphetamines.
Another former Cofidis rider, Phillipe Gaumont, accused several of his teammates and the team doctor at the time of wide-spread doping.