The diocese said in a statement that the Archbishop of Lyon, Philippe Barbarin, who is under fire over his handling of the affair, "has said repeatedly that he is prepared to cooperate openly with the investigation".
Earlier this month, Barbarin reportedly apologised to victims during a mass. According to the website of his diocese, he said he was "obliged to assume all the evil committed by some priests and personally apologise for the damage they have caused by sexually abusing children."
Barbarin, 65, has been caught up in a scandal over abuses that took place 25 years ago, long before he became archbishop of Lyon in 2002.
A priest in his diocese, Bernard Preynat, was charged in January after victims came forward with claims he had sexually abused Scouts between 1986 and 1991.
Prosecutors say Preynat has admitted the charges.
The victims have filed complaints against several senior diocesan officials, including Barbarin, accusing them of failing to report the priest or remove him from duty.
Barbarin said that when he learned of the priest's past in 2007, he asked him if he had committed further abuses since 1991 and the priest swore he had not. Barbarin said no accusations had been made since.
Barbarin has since faced other accusations of failing to remove two other priests in his diocese who had histories of sexual abuse. He denies all such accusations.
The scandal has been extremely embarrassing for the Catholic Church in France, which has worked to harden its stance against predator priests since Pierre Pican, bishop of the Normandy town of Bayeux, was convicted in 2001 for failing to report abuse.