By Julien Pretot

BEAUNE, France (Reuters) - French Tour de France rider Remy Di Gregorio has been suspended by Cofidis after a dawn raid on the team's hotel by police investigating alleged doping offences.

"We have just learnt that one of our riders on the Tour de France may have tried to use banned substances to improve his performance," the French team said in a statement on Tuesday. "Remy Di Gregorio is therefore suspended provisionally."

Cofidis said the rider would be fired if proven guilty.

A gendarmerie source said Di Gregorio had been arrested in the early hours in Bourg en Bresse and was to be transferred to Marseille, his home town.

Di Gregorio was being questioned with two other people after an investigation was opened last year into alleged trafficking of doping substances, the source added.

The 26-year-old, who won a Paris-Nice stage last year, was regarded as the next great French climber when he started his professional career in 2005 but failed to live up to expectations.

In 2011, he joined Astana from FDJ before moving to Cofidis this season.

French investigative judge Annaick Le Goff opened the investigation on June 28, 2011, Marseille prosecutors said.

(Reporting by Julien Pretot, Francois Revilla and Nicolas Burtin; Editing by Clare Fallon)