The American has consistently denied the allegations.
The judge from the Alpine city of Annecy ordered local police to investigate after the publication last year of a book entitled LA Confidential: The Secrets of Lance Armstrong.
Written by Pierre Ballester and David Walsh, the book quoted allegations by Emma O’Reilly, the rider’s former masseuse.
O’Reilly spoke to Paris police last year and has stuck by her claims, French daily Le Parisien said yesterday.
The case has been handed over to the Annecy judge who will decide after the police probe whether to pursue matters.
Last July, a Paris appeals court turned down Armstrong’s request that the book should include his denial of the allegations.
Armstrong said last week he would decide in April whether he would take part in this year’s Tour de France.